All the control servos were standard RC stuff right from a hobby shop. Used a 20 hp two cycle (big weed eater) engine. Could do fully autonomic flight for eight hours on internal autopilot (slaved to GPS). Could carry ~100 lb payload. Cost about $15k to build.
Probably do it with a $10.00 PIC microcontroller, GPS, accelerometer and gyro.
You can get a garden sprayer at WalMart for about $10.00 also and a use pickup for a few thousand..
Or, you could use a large, industrial tank and an onboard compressor to pressurize it (maybe even put the vehicles own AC compressor and magnetic clutch to use here and save about $20.00) if you need more volume..
Or, you could do a million, zillion other things for a few thousand bucks.
This is just complete paranoia, what I am seeing here..
It's amazing. I have never been so ashamed of the US.
I can practically hear people duct taping themselves in their houses as I type.