Screening and selecting tenant question

[Kexin Ma]

Hi, I am new to being a landlord. I got some pretty good applicants (at least on paper) on my first time showing the house. I have 3 questions:

1. I know there are some applicants they are not going to afford the house. But they still fill out the application. Do I have to verify their income/reference just because they submit the application? 

2. Among those who can afford the place, there are four types of people I categorize: a. working single guys. b. part-time working students (but there is one group particularly polite) c. stable family with two older kids. d. section 8 family with younger kids. In terms of prediction on how long they will stay there, how well they will take care of things, and other factors. Any suggestion who should I take first?

3. There is actually two units in the apt. I would like to hear some experience pairing clients. After all, less conflict would be better for me. 

Thank you. Any advise would be appreciated.