Here is what I would ask you, if you asked to rent my building.
1) Do you have insurance. Prove it and prove that you and the others who attend are covered
Then I would have to contact my insurance company and ask them about my coverage just incase
2) What are your plans to clean up the mess?
3) What are your plans to fix or pay for any damamge?
4) Would you personally gaurantee that everything would be as when you started
5) What times would people be attending?
6) Is it legal? Would you let the police know the event is taking place so I don't get a phone call about something happening
7) Who is in charge of any keys?
8) Are you paying me up front?
9) How can I be sure you won't leave my property and trespass next door?
10) Do you have any other building owners or property owners that can vouch for you
Those are off the top of my head.
Should I invite him/her to assist our first game, in order to supervise?
No. The last thing I want to do as a business and building owner is assist or supervise people.
You need to provide references to the last places you played. If he/she wants to they might ask to see a game.
Basically you are going to have to make it worth their while to go through the hassle.