Reserves hire civilians to go to pilot training all the time. I believe current rules say you must start UPT by the time you're 30. My rough estimate-The interview, medical, screening, officer training, etc that you have to go through first means you should begin the process by roughly 29 or younger (YMMV). That may even be a bit optimistic.
I'm biased, but its a great move for a young guy if he can swing it. Strat air is a great reserve job for building your time before you get the airline job, and an awesome hedge against furlough/income augmenter thereafter.
Good luck to all,
Capt H