1. He claims to be a landscaper. It's the winter. In Maine.
2. Whenever you ask him for his share of the utilities, he always says "Is cash okay?"
3. His cash always has a powdery residue on it.
4.When you ask him for an asprin, he pulls out half a dozen bottles of perscription painkillers.
5. You have to air out the house before your relatives visit.
6. People come and go into his apartment at all hours of the day and night.
7. These people often have vanity plates that say things like "PHISHD," "JONSN," etc.
8. Every weekend, he changes the locks.
9. There are hacksaw marks and heel scuffs around the knob and doorframe.
10. You live in his mother's basement.