However, repeating this he will quickly hit his debt to income ratio maximum and will no longer be able to get traditional financing for the next traditional style real estate deal. 

Build equity and credibility, use that plus leverage to get a bigger property with my money and OPM, rinse and repeat until I’m selling smaller units and trading in for larger 50-100 unit apartment complexes.

In reviewing banking entities for best fit on doing that (I would have a portfolio pack together that I take bank 2 bank with me to present) I would also discuss if they are a good fit for moving forward, and be direct "I would like portfolio lending, a $________ line of credit account for acquisition, from which we will later finance those questions into additional commercial mortgages in a "rinse & repeat" fashion.". 

Get onto the REPEAT part of the BRRRR

But I like @Allan Smith's suggestion of keeping him on a short leash and paying him frequently as progress is verified. 

If a past client or someone that I think will bring repeat business (of the non-reno loan variety) calls me up for one, sure, I'll help out, you can have the use of my license to further your goals.

To your question about property-specific emails, yes, I do have a domain name registered for my vacation rentals as a group, but am really only using that for my direct booking website and as an email redirect to my standard email for repeat customers.

Worldwide, repeated studies have shown that 80% of drivers think they're above average.

Cash out and repeat.

Example: I finally won a deal for a repeat BP client after writing offers on at least 6 houses in Tempe.