@David Naphy With a strong credit score you can do better than 8% on a DSCR based cash out refi today. 

DSCR loans go up to 80% of the purchase price and depending on the Debt Service Coverage Ratio and your credit score you can expect rates on a 30 yr loan ranging from High 6%- Mid 8%. 

If you want to combine two or more lesser sales into one higher purchase that is fine as long as your purchase meets the timing requirements for each sale.  

.: I haven't passed this past legal review so for what its worth: Part of my standard requirements for everyone include income is at least 3X rent, minimum credit score, say 640, Clean record and no evictions as well as deposit is paid in full at signing of lease and 1st month rent is paid in full prior to handing over the keys.

More on DSCR loans in case helpful: DSCR loans won't use your income to underwrite the loan.DSCR loans are based off of down payment, credit score and either actual or market rents so it helps to supercharge an investor's real estate goals and net worth.

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

The property value must be a minimum of $250,000 USD, and the credit score requirement is at least 700 points, among other conditions.

For example, require a minimum FICO score of XXX, gross monthly income X times the rent, and verifiable income for the last X years.

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

I also don't want to focus on one market, and not be able to score the right property for who knows how long, and then end up missing out on other locations, as being a long distance land lord is very popular as well.