The tenants so good I even lease a new unit to end same day an old tenant leaves, they have 700 scores so no one does anything wrong. 

it was my version of cash for keys - only it was more an agreement to not have their ability to rent again trashed for keys (definitely cheaper).Sorry you're dealing with this. 

I also have a credit score of 756.

This will change after the first of the year to a 30 year, 3 year balloon….620 Fico Score and 50% DTI ratio.   

Take a look at this chart: FICO Score Pct of Population Default Probability 800 or more 13.00% 1.00% 750-799 27.00% 1.00% 700-749 18.00% 4.40% 650-699 15.00% 8.90% 600-649 12.00% 15.80% 550-599 8.00% 22.50% 500-549 5.00% 28.40% Less than 499 2.00% 41.00% This is how likely a borrower is likely to default on credit extended to them.

I have been on the site for the past two days and already purchased two of Brandon Turner’s books as well as the Audible versions so I can just fully emerge myself into the world of real estate investing.

makes sense. so i actually did a 2-1 buydown FHA, i have a 800 credit score and locked in a 5.875% in today's market which is pretty damn good IMO... so the first year ill be at a 3.875% with about a $2350 monthly payment including prop tax/pmi/morg insurance/home owners insurance. lease is locked in for a year at $1400 a month which makes me only have to pocket roughly $1000. the way i see it, its cheaper than rent or mortgages in today's world!...

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

If the former, note per Union City Rent Stabilization ordinance (https://ecode360.com/15397000 is a slightly outdated version), "the terms of this chapter apply to individual dwelling units within a building, including condominium or cooperative units in the process of being converted, or having been converted".

This can result in significant financial loss and damage to your credit score.