Good places to save money are used airframes, field equipment, and engines. It's easy enough to look at airframe over and see if anything is broken, and as long as engines turn over smoothly and have good compression, they should work fine with a little cleanup. Used servos are more of a crap shoot just because electronics look the same whether they are new or worn out, and ditto for radio gear. IMO, you should never buy used batteries because their service life is so short to begin with (3 years or so usually). So search the classifieds for planes and field boxes and such, and invest your startup money in a good new radio, servos and batteries.