Several reasons: market rates, cost of operations, risks of the tenant in particular, rental history, turnover potential, loss of rent during turnover period, "hot" or "cold" market, etc.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

From recent history, mortgage rates historically are low even today, compared to the past.

If you dont have great credit, 9.5% is probably about right.

The owner owns the home free and clear, and then took out a reverse loan-HECM line of credit about two years ago.

Not sure how best to do it, but a larger first time homebuyer credit makes no sense to me. 

I’ll have $50K saved and $8,000 in credit lines. 

National savings rates have plummeted, increasingly reliant on credit cards to fill financial gaps.

Some lenders looks at age of the company and revenue (e.g. business line of credits) hence single LLC may be easier.

Once you have three done, and you continue to bring good deals, and your credit stays where it is, and you've exited all three previuos deals no problem, then now you can get 85%/90% LTC.Rates?