I think a small engine repair/maintenance could be a good idea.
At a previous employer thats what we did during the off season.
We would offer to pick up there mower then we would bring it to our shop and change the oil, fuel, and air filters change the oil, treat the gas if there was any, sharpen the blade and finally wash it up then it got delivered back to them usually in a mater of a couple of days. We did not do any repairs though just maintenance. The customers thought it was a great idea as usually they arent able to fit it in their car and all they had to do was leave it in their driveway when we told them to. With a customer base of about 3000 we would usually do around 300 a winter.
One other thing worth mentioning is the few small engine places around that are geared towards homeowners are always a month out on repairs during the fall for snowblowers and the spring for mowers. They usually have a ton of mowers waiting to be serviced in the spring.