Renter selection -- Help please

1) Single Mom with one kid, no job, claimed to have income of $150K from inheritance; no renting history, claimed to live with boy friend previously.  Has no credit card,

So there is nothing I can check, seems suspicious.  Are there any tricks from cheaters I should be aware of?

2) Section 8; single Mom 49 years old (on disability) , with a son 28 (on disability)and a daughter 23.  Seems to have good rental history but know how to cheat the system of welfare.

I have never dealt with section 8 before.

Which one to choose, or should I reject them both?

All other applications have 6-8 people and pets.

I am screening for income 3x the rent, what if the income 2x the rent? Can the renter afford the house?

Thanks a lot....