It all depends on how much are you willing to give up, also!
Intimacy is always a complicated and sensitive (not sensible!) thing. If your room-mate decides to bring someone in for the night, you most probably will have to deal with uncomfortable noises and maybe even get to see things. This may also happen: a quick run to the bathroom and BAM! there's someone you don't know in there.
Also, you can be the one who decides to bring someone in, or maybe even throw a little birthday party or so and your room-mate can be a d!ck that day.
And the rules will be set 50\50 between you and your room-mate for you will not be entirely in charge of the place anymore. It's a SHARED rent and the other person will also be entitled to have a say.
It depends on how much you need that extra cash and how much are you willing to give up. I live alone and it's the best thing ever! I clean if feel like it (no one cares! The place is always clean, BTW... but If I want to clean late at night I can do it), I love loud music, I don't work on the weekends so I get to sleep until I feel like it all through Saturday and Sunday and no one bothers me.