Established labor unions already have large-scale financing for their activities, primarily (if I am not mistaken) through borrowing from pension funds. But smaller unions seeking to organize have to rely on private initiative or, in fortunate cases, modest contributions from sympathetic organizations. Imagine, then, a bank whose sole purpose is to provide financing for labor union organizing, and structures its interest rates and lending policies to continuously increase the amount of money available for that mission. A given number of specific efforts may fail, but if loans are made intelligently, the financial ecosystem for labor organizing could still be grown over time.
Disclaimer: This is speculation on my part, and I yield to anyone with professional experience who finds fault in anything I say here. I am merely exploring an idea and putting it out there for discussion, not claiming to have found an actual business model for such an endeavor.
First, allow me to recognize that this is probably not an original idea - there is far too much history behind labor organizing for someone not to have already conceived of a bank to finance it. It would not surprise me if limited organizations already exist that perform this function on some level, although my guess is that these would primarily be instruments of large, established organizations such as the Teamsters and AFL-CIO. But I am confident that, if such institutions engage in "entrepreneurial" financing to support nascent labor movements, it is not their primary function, and does not occur on a large scale or regular basis.
Let's take one of the biggest non-union jobs that should logically be unionized: Food servers (i.e., waitresses & waiters). It has a learning curve and (I'd assume) occasional stress attached to it, but it is not really "skilled" labor - most people can learn to do it proficiently in a relatively short amount of time. As a result, the pool of potential hires is practically unlimited and continually turning over as younger people enter the work force and older ones find better opportunities. This creates a labor monopsony - supply is vast while demand, though numerous in absolute terms, is comparatively small, so employers hold all the power. There is thus no negotiation in establishing the terms of a food server's employment - the employer sets the term, and the employee either accepts them or walks away with nothing.
Suppose the servers of Restaurant X decide they are due a raise: Business is booming both at their location and generally, the CEO is swimming in bonuses, and the stock of their parent company is doing very well. They send management a joint ultimatum, signed by every single server at that local branch of the restaurant, requesting a pittance - a dollar per hour raise - and threaten to go on strike if it doesn't happen. Management ignores them, and as threatened, they go on strike. What happens next?
What happens is that part-time workers from other locations are brought in as if nothing had happened, the strikers are fired, and they have no income to sustain a drawn-out demonstration that would damage business for the company. The strike is thus "interpreted" by the economy as a job opening for entry-level workers, and not as a failure on the part of employers to pay adequate wages. And even this is a pretty rosy scenario: Getting all servers at a single branch to cooperate would be quite a feat, and management could easily offer time-and-a-half to a handful as a bribe to break solidarity.
Unfortunately, "scabs" cannot be blamed for accepting such bribes or doing work that breaks strikes - in most cases, they have no choice: They need the money, and they take what they can get. This is where a bank would come in handy: It would treat labor strikes as investments toward the future income of the employees, and provide enough up-front support to striking workers that they could drive off business with obtrusive, sustained demonstrations.
Potential scabs could be preemptively bought off to agree to work and then just not show up, or better jobs found for them, allowing them to quit just as they're needed. Workers could be given audio recorders and legal counseling to keep records of the threats and illegal tactics used against them by management. Local media could be sold on the story in a way they find appealing, rather than just waiting for them to pick up on it and then being predictably disappointed. A large number of potential actions could be taken in this respect, but what makes them all possible is having a ready pool of financing available.
Now, the likely victory of the waiters and waitresses of Restaurant X would probably not repay the expenses put into it - it's just one local branch, and as a strategic matter, it would make sense for their demands to be very modest. But it would get attention, both in other branches of that restaurant, and in other restaurants: Food servers would see what was happening, see what was possible, and become interested in what the bank was offering. After racking up some modest, strategically-targeted victories, the resources of the bank would build up and more formidable objectives undertaken.
My first-run thought would be that the bank would offer its support in the form of loans that only accrue interest in the event of victory, and whose payment structuring is directly indexed to the size of the advance in employee position (taking into account benefits and costs of living, etc). Workers who lose their jobs or are forced to accept shitty terms wouldn't have to pay a thing until they're in a better position, and then would not have to pay interest because the funded effort would have failed to benefit them. In other words, the whole thing would be structured to minimize the risks taken by workers in seeking to organize and demand a share in the prosperity of their employers.
Not everything would be funded - some industries, some job categories, some geographic locations will simply not be suited to labor organizing at a given time, so the bank would have to pass on supporting initiatives arising there beyond offering advice and training. But being selective would make the overall effort more likely to succeed, allow the bank's pool of funds to grow, and increase both the size and power of the labor sector over time. Given sufficient growth, this would allow labor to once again be a strong voice in politics, and force reforms in areas such as trade, health care, and others that have been dominated by employers since the Reagan era.
As to the structure of such a bank, I would say it should be for-profit rather than non-profit: A non-profit is generally self-limiting, and lacks access to the resources of a for-profit institution that is able to prove it can make money. However, it should be chartered such that profits are only possible by producing benefits for the individuals and organizations who borrow from it - no mortgages, no home foreclosures or repossessions, none of that predatory shit. It acts as a venture capital firm for labor unions, treating them as businesses and additional income to their members as profits. In exchange, it gets a cut of those profits up to a percentage above the initial investment (or perhaps on an ongoing basis, if that were found to be more practicable).
The beautiful thing about such a structure is that it becomes more profitable with volume - i.e., it benefits from economies of scale - precisely because the amount of money involved with each individual worker is relatively small. That means once you overcome the initial hurdles, economic inertia is on the side of growth - you have a larger and larger pool of prosperous workers paying into a pool of funding to finance the organization of less fortunate ones, and the imbalance of financing between striking workers and employers becomes less and less significant.
We often get caught up in the morals of the labor movement, forgetting that a strike is fundamentally a money-making enterprise: You're engaging in a strategy to increase income. Don't run from this fact - it may give workers strength to feel themselves on a righteous crusade for justice and human dignity, but there is no reason they can't also make use of the same cynical business instruments and strategies that their employers use against them. Large industries faced with labor strikes often have the support of giant banks to finance their operating losses, and even mid-sized businesses tend to have more than enough equity to borrow their way past anything their employees can threaten them with. Why not even the odds?
The largest hurdle, obviously, is getting started - something I have neither the expertise nor the intention to try (again, this is just an idea). But really all you need to begin is enough money to meet federal and state regulatory guidelines for initial establishment, and to afford a set of small, local labor strikes resulting in enough net revenue to afford the next set. That's not peanuts, but it's doable for a number of organizations. Ironically, labor could very well follow the advice of the supply-side cultists who hate them and "pull themselves up by the bootstraps" - start small on the local level, and then spiral upward while responding flexibly to the evolution of new anti-labor tactics by the corporate sector.
Obviously, such an institution must never be publicly traded on the stock market. The specifics of ownership and control would be for the people who actually build it to decide, but it should be calculated to minimize opportunities for corruption, fraud, or perverse incentives on the part of management. Off the top of my head, I would suggest rigorously-enforced oversight by a nonprofit labor-advocate entity, or at least some similar measure to ensure the tail didn't end up wagging the dog. But this is just one supposition piled on to another.
In all likelihood, there are probably already databases full of feasibility studies and market analyses on this subject, and perhaps paper graveyards full of failed attempts - I have no clue, and haven't found the proper search string to find any answers from Google. But I do know that being stymied by the assumption that things have been done before is a recipe for making no progress: Ideas have to be tried, and tried, and tried again, though of course with as strong an appreciation and respect for history as possible.
So perhaps if there are liberal MBAs out there, they can take a look at it and see if there isn't some self-sustaining private sector way to rebuild the middle-class through a labor-financing bank. I'm sure it's difficult, but there is always a way, and finding it will make reforming Washington a lot easier. As Archimedes might say, leverage is everything.