I'd start with local free advertising, this year if you can just to get your name out NOW. If you want to spend the bucks go for handouts, for sure! As for the 1% respondents, you'll more than likely only get about 10-20 seasonal clients.
My busiest was 23clients a week, and I work full time. I'm down to 11 a week, which is more manageable for my schedule now, but anyway, I can do all my 11 yards in a day. Most take 30-45minutes each, including traveling time if I do them on my own. If I get my brother to help me out we can shave 3-4 hours off that time.
I was going to get a 48" WB this spring, but due to trailer costs I decided against it for now. I run anywhere from one to three 21" WB mowers. If I go out by myself I'll only take one mower of course but I can cut down each visit to 10-20minutes having two guys cutting and myself trimming and tidying up.
If you wanted to go all out full time, once you get the client base, you can put in 10hour days 4-5 days a week and net a couple hundred bucks a day, or gross around $350-400. If you charge $25/lawn, that'll be less of course.
After I factor in vehicle and trailer maintenance & fuel, business taxes, license and insurance, not to mention labour expenses I'll net in 30-40% of what I gross, which is high for the industry, but my equipment is rather fuel efficient and maintenance friendly. Everyone is different too. I only advertise for a few weeks during the start of the growing season here in Ontario, then I fill up my empty client slots and perhaps gain another 1-2 folks in the process.