The customer/borrower will have a contract with the contractor, in addition to the HOCA (Homeowner Contractor Agreement). 

I have conducted my due diligence (license and referral checks and current project inspection) on contractors that I'm about to hire just to find out that the plumber doesn't offer W9 to customers.

Find one that does not have a high-priced long-term monthly contract, flexible pricing, and excellent customer service.

Only store staff uses the bathroom, not customers.

then sell it to your customers and if they decide to move forward they become your client?

No government agency have instructed any bank that the "Customer Identification Program" means the business must be incorporated in any specific state.

I hear what you are saying about somehow qualifying the audience- something to think about for my next "get you new customers" idea.The goal here is to offer an alternative to the traditional marketing methods...postcards, newsletters, ads, etc.Your chances of turning cold leads into warm ones are much higher with my model, if you were to be on site during the event...shaking hands, making intros, sharing a drink or two, etc.

Be careful with the assumption that your M-I-L's difficulty in finding a rental indicates a "strong" demand for rentals.  

I see a lot of assumptions / misconceptions about my personal situation in the responses so I’ll try to clarify a few — obviously language isn’t perfect, certainly my choice of wording isn’t, and I also didn’t want to write a full dissertation about my personal background [nor make you read it] before starting.

So I'm going to make some sweeping assumptions about you to offer my next set of advice.