they're actually pretty good. I did the same thing and went to a prep school this past year and I didn't apply to the AFA last year, but I did this year as a backup to USNA and it looks like I'm gonna get in (even though I've already gotten into USNA so I won't be going to AFA)
I paid my way through btw and wasn't on scholarship, which is what i think you're saying you want to do.