I would automatically assume he was a drug dealer. I would never do it.

Everyone gets screened - everyone, no exceptions. It has been my experience that the only people who wave money under my nose are the people who will not pass the tenant screening, and who have something seriously wrong in their background.

So. You take this guy's money. One year in advance. Three months into his lease the neighbors start moving out because of the loud and disruptive behavior, and the partying all night, and the vandalism of their cars in the parking lot. Or else, the police kick in the front door and haul him, his buddies, and the evidence of the meth lab off.

Well, what are you going to do about it? You commence eviction, he and his lawyer show up in court; "your honor, my client paid his rent a year in advance. That he is having difficulties now does not give this pond scum sucking landlord the right to evict. Clearly this landlord is trying to evict only to pocket my client's hard earned money."

You are asking for big trouble doing something like that.

I am sure there are some legitimate circumstances where someone might have a good reason for making you that kind of offer, but in 20 years of running rental properties - up to a few hundred of them at a time - I have never (and I mean literally NEVER) run across an applicant who had a good, legitimate reason for waving money under my nose at application time.