I think the economy is going to hurt you, plus not sure what your comp. is, around here we have a ton of Mexi's that will mow for $10.00 a yard.
In the same area we have a retired teacher, about 60, drives a new Tundra, small 6 x 12 with a 34" rider and a push mower and mows about 20 to 30 yards a week.
He the type if he gets the job fine, if not he doesn't care, so he must have a great retirement.
Look into roof washing.