How Do You Qualify Tenants For L/O

Besides the obvious of doing a background check and a credit check, what else do you do to qualify a possible tenan/buyer? I have been rehabbing and selling, but have a property that I may want to L/O. Most of the people coming to look at the property have terrible credit. How do I use their credit to qualify these people? With lack of credit, how else can I qualify these people? Should I ask for references, including their current landlord? What if they are in a house, but need to move (no landlord to contact). Thanks; John Walko