"I'll pay the rent for both of us, and then you can give me your half of the rent." Eventually, this situation evolved into (or was manipulated into) "I haven't had much work this month, so could you give me your half of the rent plus x percent of mine?" (where x increased x-ponentially!) I should have foreseen the day I got a call from the landlord mentioning that my boyfriend was several months behind in paying him the rent.

Funny thing... after I moved out, I found I had more "mad money" left in my budget even though my new place had a higher rent...