I know there are self rental rules but having two other individuals with formal rental agreements would that change anything?

I would require a formal inspection on the property.

Write it up as a formal lease violation, giving them 30 days to remedy. 

It runs differently, and, if you are taking other people's money, you had better know exactly what you are doing.I'd recommend stepping up to some formal education. 

The Pros are that 1) he does not ding your credit by checking it, 2) he does not saddle you with the debt, 3) you build a relationship with him on paying on time, so that he may wish to sell the property to you at a later date, formally where you take out a loan.

She sent a "formal request" for her money claiming that I didn't spend 6 hours.  

I’m pre qualified @70K based on income and OT, but I don’t think I have formal preapproval.

The fact that you declined someone is a risk by iteself, legidimatly or not - if you never formally decline anyone, you eliminate the risk.

Refunding the application fee also helps to avoid push back or even worse, a formal complaint based on real, perceived, or imagined discrimination.

Yes I'd work with him tell him you want partial payment tomorrow, and get some money on the books,, I'd still give him the pay or quit,, tell him this is formality that you are willing to work with him but if things fail you will be left with no resort if he does not pay or agrees to vacate by end of month,, And remind him Dec rent is coming up..