Been pressure washing just over a year, a great move provided you buy decent equipment ( as with anything really )
Don't fanny about with anything less than 19 lpm - honda gx390 is the dogs danglies for entry level commercial work.
Best deals, advice and service is from qwashers (q services) you can find them on eBay. Great starter packages.
earning potential p/h is well over window cleaning, but it's a one hit wonder type thing
Darran