Please keep in mind that there is statute of limitations in each individual State for any criminal offence committed in the past.

He has sent a copy of criminal background check from his home country saying no records of criminal history found ... not sure how much weight that carries.

My night job is a winged superhero protecting Gotham City from criminals. 

His criminal and credit history are borderline but passable.He says that he really wants to buy the whole duplex but would like to rent one of the apartments for a year first.

Further, that there were entire courses and clubs dedicated to teaching these criminals how to con you out of your house, your money, and your first born child and run away before you knew what hit you.

For a criminal background check, go back 5 or 10 years.For residential history, 3 years should be fine.If someone is starting a new job when they come to town, I verify their current and last employer and call the company that just hired them to make sure they actually have a job.

He doesn't have criminal background. 

@James Wise  What was described above is simply life in the rental bizz  no amount of up front screening etc will keep you 100% immune from peoples lives.. as lives change.I had 11 A class ( new builds ) in Jackson MS area.. and by and large they were great I could self manage those ( self being my secretary managed for me).. but even there on brand new 200k homes I had one completely destroyed.. 50k in damage... and luckily the insurance company covered it and went after the tenant for criminal charges... as you know normal turn over damage is not covered with insurance.. then I have owned C class Section 8 with the same tenant for 8 to 10 years.. just like many others.. its one reason I subscribe to the thought process no matter what were or how.. you want some scale if you want to be in the rental business.. however you can do it get to at least 10 doors as quick as possible.. that way one bummer does not sink the ship.

Everyone knows Detroit is only filled with criminals and corrupt politicians. 

That usually gets them moving on the documentation if they are really interested.To save time and money since we don't require an application fee, we tell everyone upfront that we require credit/background/criminal checks security deposit and first month's rent in certified funds before lease signing.