Someone beat me to the reality check.
Everyone's situation is by definition unique, and human relationships can be complex . . .
However, the OP has to be aware that there are a lot of guys with very little . . uhm . . . whats the word? Scruples?
So there might be a lot of guys in the house that will regard you as a little sister type to be protected and amused, but there are also a lot of dorky desperate guys that will take whatever they think you are freely offering.
And fraternities in general seem to attract more than their fair share of dorky desperate guys.
Also, if you are thinking of the future, a lot of higher status males won't want much to do with you if you have been passed around 2 or 3 of their brothers, especially if those brothers are much lower on the social totem poll than they are, which is probably the case if they are messing with someone still more or less in high school.
I have seen that happen where an otherwise pretty, intelligent girl will be skipped over by guys because of who she used to date or fool around with.
As far as how it will hurt your Rush . . . Come on. You are a girl. You know the deal. Girls are looking for reasons to love or hate you. Hanging out and partying with boys they know (and maybe sort of regard as theirs) seems to always get negative feedback.