If you just need a little bit of work done for you, then check out the job shop listings at
If you are serious about buying, then maybe you can find a used OMAX
2626 machine, which has a cutting area of about 26" x 26". New, the machines go for about $80,000 with everything you need to actually make parts (installation, training, controller, pump, xy system, abrasive, etc.) Used, maybe you could find one for cheaper, but right now the economy has just picked up, making used machines a rare item to find. (In fact, you may even find you have to get on waiting lists for new equipment.)
for more info on the above mentioned waterjet.
Rental units are also available, along with traditional financing, etc. I don't know what it costs to do this, though.
Really cheap waterjets (