The only additional thing being in UHC as a freshman will do is get you into UHC housing your freshman year. And even then, the UHC Freshman Dorm (Sutherland West (I think)) is so big that you don't have to be guaranteed UHC to get into it your first year,. (just email UHC and ask if you can apply anyway).
As for classes, anyone can take UHC classes as a freshman as long as you ask permission. After your freshman year, as long as you maintain a 3.0 (I believe, may be 3.25) you are automatically "in" the UHC, can apply for housing, and sign up for classes without permission.