Were is the best place to rent a camping tent and how much does it cost?

I am haveing a camping party in my back yard and would like to rent a tent that 5-6 people can sleep in.

Gosh. I’m not sure where you are located but REI used to rent such gear, but I’d try any local sports/outdoor supply store to ask them.
This would be the kind of gear you either just buy or borrow from a family member/friend/neighbor.
Have fun!