LOL, I keep thinking, wow what a gig. You drive to someones house, use their water source, prep and blast a car in 30 mins, then get $1000 dollars, and leave while telling them the clean up is their problem.
No shop overhead, no employees to pay, just a truck and a $10k machine/trailer. Let's see say 4x a day, thats $3840 after material per day.
Go blast 12x a week, that's $11,520. Machine is paid off in week one. Truck is paid off in week 3. Then all profit.