I've just spent like 20 comments doing so. Short version: labor and resources.

> Will the bank be loaning them painting hours?

Tangential to my point, but I'm happy to go into details on how this might work. Effectively various forms of labor would have a known cost (set by labor markets) and various resources would have a known cost (beyond the labor to extract them) derived from some social price-setting process (we can just call it "democracy" for now). So if you make widgets, you'd have to demonstrate to the bank that you can do so with X resources (at R cost) using A labor at L price, and together the total cost being N (remember, we can add R + L because they both have a price value either set by labor markets or by democratic pricing, ie a common unit) and you'd have to demonstrate there is a social need for your widgets at R + L cost. If you can do so, when another company orders 100 of your widgets, they take on the disaggregate cost of your widgets (100 * (R + L)) and that cost is removed from your company's costs. So although the costs are reducible to a single "price" (an at-cost price) which can be used for effectively limiting a company's upper ceiling on costs, the actual disaggregate costs are the ones that are tracked and passed through the economy until purchase by a consumer, who is able to inspect and act on the disaggregate cost (but pays the aggregate price as a single number). Yes, I know what you're thinking, shortages, clearing prices, etc etc. Short rebuttal: the consumer might not pay the actual at-cost price based on a set of automated incentives the company follows to limit shortages or clear inventory.

So back to your question, the bank might loan them a total aggregate amount that they can spend to acquire at-cost items from the economy to transform them into widgets, at-cost.

Happy to expand...and forgive me if I've been short, but the number of people engaging who are automatically assuming I want slavery or don't know how markets or prices work is making it difficult to separate good faith from bad.