However, this is a situation when they deny that their partner has moved in but it appears like they live in the apartment building.This may happen because of bad credit or because of criminal convictions that they do not want to disclose.

Had somebody throughly checked this guys income credit and previous references he probably wouldn't be your tenant today. 3rd.

Just put them on bad credit.

I have less than perfect credit and pretty much no cash to put into the deal with a hard money/private lender/crowd funding.  

@Jeremy PhillipsFinding Private Lenders is easy when you have a Transaction with high profit margins and you have High Experience with a Track Record to Show.

Can anyone refer me to a good online credit/background check.

I've heard to do back ground checks and credit score checks.

I use Cozy for credit/background checks.  

I personally scrubbed each lead on my list because I didn't want to waste any money on properties I wouldn't be interested in (i.e, the property is in a bad area of town, near train tracks, etc.).  

We have excellent credit and have already lined up with a Hard Cash lender.