If you have a salesforce and/or have a labor force that lets you do the sales, if you spend the time getting through the redtape to find the right person to talk to, and you are willing to do some single unit cleanings to get your foot in the door, you don't need a service company like Tech Wash. Your expenses are going to be higher but you can get a higher price.
If you are an owner operator trying to get your feet wet with some steady multi location commercial work, a service company may be your ticket. Keep in mind two things. A service company can be out there selling on price. Then they are also gonna take a cut.
Chris, I didn't know you did work for TWS. Bad experience?