Started out with a 21" MTD high wheeled with self propelled function disabled. I got it for free from my Ex girlfriend's parents (they bought it for $5 at a yard sale) because it didn't run. I put a brand new $30 carb on it, new spark plug, and changed the oil. Fired right up on the first or second pull from then on. Had a ryobi expand it straight shaft string trimmer, hedge trimmer, and edger. Also had a Homelite handheld blower. This was all stuff I was using on my personal yard.
3 years ago I bought a used 36" Snapper Pro gear drive walk behind for $1,000. That purchase really increased my profitability compared to a 21". I Still use it today, but I'm planning on buying a new one (36" Snapper pro hydro SW20 model) in the spring. For the first year, I used ramps and drove it up into the back of my truck. I bought a 5x8 trailer beginning last year.
Here's the current snapper
I'm only a part time operation and have been slowly expanding customers and equipment over the years. All of my equipment was bought with cash. I sold the MTD 21" last month to my old roomate for $20 since he just bought a house and was looking for a cheap push mower to mow his lawn. I sold the old Ryobi at a yard sale last weekend for $20 (Still ran fine). I picked up a 21" Snapper hi-vac the other day off a guy on craiglist just to have a 21"er in case I need it. I rarely, if ever use a 21. The 36 will go most places and whatever it doesn't get can be cut with a string trimmer.