Start out with the traditional criteria (3X rent for income, good credit, no criminal record) and go from there.

There is something about being in a 8'x 8' room for 8-10 hours a day that made me feel like I was slowly dying or that I was a criminal (at least my cell had windows).

If they are long term tenants and just want to stay put you may be ok, but I would think finding tenants without criminal backgrounds and even decent credit that pay on time to be difficult in this area.

Now, it is possible they won't abide by the lease, in which case you'll need legal help (not the cops, they don't enforce civil contracts, only criminal law and court orders). 

I believe you can do prepaid credit cards through your bank, but that involves paying interest on your own money or something daft iirc.As for the immigration process, it doesn't take into account credit ratings or score or bad debt from your home country.However, it does take into account criminal records and drug use.

Chelsea Tustison, I would seriously consult a criminal defense attorney before you get yourself potentially into trouble.This old woman has confessed to you that if you help her she will commit two federal crimes,tax fraud and social security fraud.She wants you to pay her cash that she has no intentions of declaring on her taxes and she will continue to receive social security benefits she would no longer be eligible for under the current regulations.If she gets caught in the future guess what,her defense attorney will lay it all at your feet."

So, my primary factor is job history & criminal history.

Verify employment or source of income, criminal background, emergency contact.

I let them all apply but usually most people won't apply once you tell them we do credit, eviction, criminal, job and salary checks.  

Check everything including credit, criminal, and eviction and set strict standards.Good luck with your venture!!