The story behind this guy was he had an extra property that he had to kick his son out of because of drugs and such.I asked him if he would sell it for what he owed on it and he said yes.

A medical fact I know from the Army, no one is immune.Check your diet and cut back on drinking if you drink beer or booze.Take a sleep aid as prescribed and tapper off as you get use to sleeping better.You should really mention this to your doctor, there can be other issues you're not aware of.The older you get the less sleep required, I get 5 to 6 hours, I will also take an after lunch nap for just under an hour, but not always.

do you think this would attract that type of tenant who is possibly selling drugs or doing other illegal things?

While I won't defend him on run down rentals I think it is unfortunate that society wants to hold him responsible for vacant properties and drug trade which he did not create.

It is the reason my Mom and Dad got divorced when I was 3 yrs old was because of his drug and alcohol issues.

Is it illegal to ask potential tenants if they can pass a drug test? 

I happened to have the criteria of no previous evictions as well as no smoking and no drugs. 

If my health was my highest life priority and I was diagnosed with a serious illness would I take drugs?

Overall violent crime isn't a big factor here, but there are pockets where there are a lot of drug users.Overall, like any investment, I would make sure you are familiar with the area you are buying in before you invest.  

(Because they don't want to get a license, or they can't get one).Sort of like, hey, I'm selling the briefcase, not the drugs inside of it!