I have mixed feelings and ideas on using my equipment I buy to do work for others that pay me to do it so I can recoup my investment. I had tried things like that in the past, so I could justify buying a bigger or better quality item, and then hire it and myself out to make up for it, with mixed results. I usually wound up working more than I had wanted to, and put excessive hours and use on the machine, to the point that it would have had on it if it was used just for my use. Lots of times it cost me more in the long run in maintainence as well as it ran up the hours quicker.
Just be aware of your warranty, as some have a different time frame for items in commercial use than they do in residentil use. My pressure washer had a 1 year warranty for residential but 90 days commercial. Pumps and engine parts especially Honda parts are not cheap, and $hit happens. Seems like most of thre larger commercial washers have Hondas or the 2 cylinder B&S engines.
Liability is another issue, make sure you have it covered, because as I stated before $hit happens.
Will you run into any problems with needing a business liscense or permit? These type of things can crop up if you physically advertise with flyers and the wrong person happens to get ahold of one. Thats a very common problem in my area. We have what is called the Bulletin Board, which is a weekly mag put out that lists items for sale, wanted,trade, and services offered. Its free to place an ad n the mag, and it costs 1.25 to buy it. Its a very hot mag around here, but city officials seem to like to also as it allows them to zero in on individuals engaging in business without the propper paperwork and permits etc. So if yo put it in writing in regards to flyers, etc it could be a total different ball game than just word of mouth.