It's not the fact you can't afford rx7, it's insurance that'll kill you. I was looking into 2003 911 and I contacted my ins agent and he started laugh, usually that means I'll be payig $$$$$$ (surely it was $1,800 a year) and I'm in the 30's married with kids.
Word of advise, DO NOT get pre modded vehicle of any kind. You know the car went thru hard driving and you don't want to go into serious work done soon after you get it.
Stick with 4 seater helps a lot if you're considering ins factor. If you really want rx7, I know you do
go with N/A as turbo charged vehicle tends to add more $$ on your ins.
Or, better yet, list up the cars (realistically) and compare ins rate and go that route. Afterall you'll be paying similar rate until you're 26 any how.
Good luck and hope rx7 will fit into your toy budget (pmt & ins & gas & maint).