You can, as far as I know, but it may not be a good idea. The landlord/tenant relationship is a business relationship and renting to a friend could blur that line and lead to difficulties should you have any problems with the tenant. You could lose a friend, and there is no amount of money that can compensate one for the loss of a friend.
My advice is to mke sure you qualify the tenant as you would anyone else, get a background check including criminal history, eviction history and a credit report. Make sure they have enough income, combined with their Section 8 voucher, to afford the rental unit. And, if you do rent to them, inspect the rental unit regularly and insist that all the rules be followed strictly.