Manuel that is a very good question.
Common sense does dictate a red flag and you are right to ask pointed questions to assauge your fear.
That said, not all same city guests are a nefarious lot.
Some people may have been transfered and 9 miles in LA can mean an extra hour commute.
Some people may be flying out and want to be closer.
Some people want to check out a new neighborhood.
Some people are getting separated and need a quick place during transition.
(Of course, I talking about a reasonable separation transistion, not the immediate crashpad needed after a blow-out... That situation is more for a hotel.)
I have had very good luck with same city guests. I hope you will too