There's a few different ways to focus on a lower rate such as with house hacking and making the investment your primary residence, requesting a significant closing credit from the sellers for standard rate buy-downs (which I've had great success with recently), or utilizing lenders who offer short term rate lowering solutions such as 2-1 rate buy downs (again, ideally paid for by the sellers).

I make sure I screen each potential tenant thoroughly (background and credit checks) and require references.

I'm broke as a joke but I have good credit how do I get started 

I agree that the algorithms favor most favorable nation pricing.  

No social or credit pull needed upfront. 

A line of credit won’t commit you to a monthly payment unless you use the money, so you can avoid paying interest when it’s not in use.

This includes credit, criminal, and rental history checks for all parties.

A cash out refi should take 2-3 weeks with most lenders, and you should have only an appraisal a credit report fee as upfront costs. 

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

-Max LTARV is typically 75% -Is a 12-24 Month Interest-only loan with a balloon payment - Minimum credit score is typically 600 -Interest on the Rehab is usually paid per the total drawn amount.