We suspect drug use, but obviously can't prove anything. 

The seller's attorney does not care where you get the money be it cash, financing or drug deal. 

@Romeo Kaado how are you im currently planning on attending a real estate class for my liscence,but due to my criminal past im scared to lose my money because the real estate commission is not giving me a sraight answer.My history only consist of drugs distribution,no sex charges,no violence, no theft,no robberies,nore fraud.Will that disqualify me from getting my liscence because i cant really afford to lose 400$

We list no violent, sexual, or drug convictions and that we have the right to refuse to rent based on any felony conviction on our postings.

You are exposing yourself to potential liability (neighbors with kids) and damage to your business (that guy rents to sex offenders/drug criminals). 

I've already given drug screens to 5 people going there for work. 

I once had a perspective tenant apply looking professional and nice, while on social media we could see what type of lifestyle he led (non stop partying and drugs)   You need to be careful why you say no, but finding red flags can sure help narrow down the search. 

Its the gate way drug to owning mobile home parks in the near future.

Its the gate way drug to owning mobile home parks in the near future.

I don't know the situation that occurred in the OP but if you can alleviate at least one of the above and one of these parties knows what they are doing you will be ok.