Max,
What style of wash are you building...barn (people pay for time in the barn) or individual bays (where people drop
coins in the coinbox)?
Barn style I would use regular central vac type machines (check out the ones at Big Buckets Car Wash).
Coin operated I would use vac islands. Up there you will likely charge 75 cents to $1 per minute and that's way too expensive for vacs, so you would need equipment that can recalculate time at a lesser rate when you're switched to vacs. But then do you want people in your bays washing at say $.75/min or vacuuming at $.20/min?
Hope this helps...Big Leo