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

We had one young lady, good job, good credit, good rental history but she had poor taste in men.

I invest in mid to upper-income areas where good credit scores and high earners aren't hard to find. 

If you have a seller finance note for $2k/mo and make $4k/mo then you have a DTI of 50%...it won't be on your credit report, but is a debt that needs to be disclosed.

Just gotta be real with them :D Let them know you will try your best to have seller cover all of some of the closing costs.Can also always offer above asking price and ask for the difference as seller credits

If we had a GC with a solid track record, I'm confident I could find the capital.

We use these factors in this order of importance (feel free to create your own):1) Tenant pool credit score2) Location => Neighborhood3) Property condition & amenitiesClasses are not defined for the SFR industry and are relative to the area.

Does the broker have a solid track record?

I send tenants to collections because I get the comfort of knowing it sits on their credit report for many years and prevents them from getting loans or cheating another landlord.

Using a company to do rent reporting to Credit Bureaus is a good idea to prevent the delinquency in the first place and at least increase leverage to recover the unpaid rent after it has happened.