Deposit for roommate

[Derrick Lloyd]

I have a 2 bedroom/2 bathroom primary residence that I bought with the intention of renting out the extra room.  Originally I had a friend renting from me for about 2 years, and there were MANY lessons learned.

This time around, I plan on having a required deposit, but not sure how much it should be.  I think 1 months rent would be a little overkill since they will just have the room and bathroom (rent will be $900).  Is half a months rent a good number?