Age Difference

I know there's lots of joking around here about lolis and pedos and whatnot, but, seriously, what is the biggest acceptable age difference?  Lately, I've found myself attracted to my friend's sister.  Thing is, I'm 24 and she's 18 (freshman in college).  I feel kinda bad about it.  I feel dirty just for thinking she's cute.  And I'm not all "zOMG she's teh hawt I wanna sex0rz her," I really like this girl.  Should I feel bad about it?  Should I try to persue something with her, or just get over it?  Would my freind get mad at me for going after her little sister?

>>9
The fewer people you hurt, the fewer people are going to be trying to kill you in years to come.
But I think the point behind this particular bit is that if \ a 18 y/o is trying to get with a 50 y/o they're either after money and thus will be nothing but trouble, or the have issues with their parents and the 50 y/o is going to have to deal with their partner screaming "fuck my daddy/mommy" durring sex, and if a 50 y/o is trying to get with a 18 y/o their probably looking for someone to scream that durring sex. It's not likely to be a good experience for anyone.