What’s the best way to determine if a lender specializes in conventional, commercial, hard money, non-QM, or DSCR loans?

This sounds like a solid return!

Cash flow is mostly non-existent now, unless you find a great deal. 

But since it was being used for investment when you sold it you also qualify for a 1031 exchange.If you find that you still have any taxable gain leftover after the primary exemption, then you can indefinitely defer that tax and not have to recapture any depreciation in a 1031 exchange.

That means either you won't cash flow or your Return on Equity (ROE) will be terrible.Since this is your primary residence you'll be exempted from paying capital gains taxes when you sell.If you sell to your parents, it will be considered a non-arms length transaction and will get closer scrutiny.

Your reporting on your federal return shows whatever recognized gain is recognized. 

Of course, with private lenders, you must give up equity or a return on the debt.I agree with @Jonathan Greene that the BRRRR market is difficult right now.

What exactly would make a city board approve non-affordable (i.e. not Section 8)  apartments?

My list was rankings by dollar amount and number closed Nationwide for past four quarters for NON QM lenders that do DSCR.

Not what we are looking to do and all the MLS listings just don't pan out numbers wise so far.That's awesome that you got some returns on flips and found some buy & holds recently.