Harbor Freight and Eastwood both sell low-end kits and powder. Use Berryman's B12 Chemtool for cleaning parts before coating (acetone would be better but pure stuff may not be easy to locate), and buy some gloves and a particle mask. Price those items and you'll know your start-up costs.
the harbor freight one is good, but a sand blaster is something to get later on, because if you get a sand blaster you'll almost certainly want a booth for it and those are like $150. You can clean parts with wire brushes and de-kote (eastwood) to start out with, then if you really get into it get the sand blasting equipment.
If you are shoppping at Harbor freigh, wait for sales, you can get some of the stuf @ 1/2 off.
I bought the air bursh pump WITH REGULATOR and the powder coat kit and have been very impressed with results (especially for about $120). I have not needed to sand blast to get good results, but make sure you sand and prep well using a prep solution..