What he did, by jacking up teh price with the extra rommate is pretty common. My parents have a couple of rental properties, and if it is a two bedroom, and one person lives there, rent is 700, if two people live there its 1000, doesnt make sense to me, but that is the way its done. I think the earlier suggestion, was the best: gather up your other roomates, and see if they want to help you fix up the place, in exchange for the landlord for lowering the rent. If you didnt sign a lease, and dont want to go through that bull, move out.

also: ditch the 5th roomate, and build a bar in the basement...duh.