I own and operate a mowing business. We do all sorts of work. From Highway right-of-way mowing, to large acreage properties for a variety of land owners. I've mowed for real estate developers, home owners associations, legal conservators who're managing property for elderly in nursing homes, and even just plain ol' Joes who own a few acres but don't have their own tractor.
Getting started; It is a SERIOUS mistake to go into this line of work without adequate insurance. Also, you need business license in some areas, along with tax liability, possibly employees (and all that goes with THAT) commercially licensed and tagged truck/trailer, ect.....ie, run it as a legitimate business. Most "big ticket" customers will require proof of your being legal. You know the drill.....
Then you hit the streets and compete with already established mowing contractor, as well as the guys who risk it all (without being legal) for beer money.
Smaller jobs that can be done with relatively small equipment USUALLY end up in the hands of the beer money guys. Go after the big jobs and you better have big equipment and the operating capital to carry those jobs for long periods of time. (Some state jobs I do, it's 3+ months before full payment is in my hands) Quite a few of the state/local municipal contracts require performance bonds. Even with a bonding firm, you'll need a percentage of that from your own wallet.
Equipment will take a thrashing. Mowing highway ROW's is some of the most dangerous work you'll encounter. I've had 4 tractors hit by cars/trucks while they were mowing, 3 at a considerable distance from paved roadway. Also had 2 trucks destroyed when motorist's ran off the road and struck them. Then there's the occasional man hole cover, sawed off telephone pole, car rim in the weeds, car battery laying in the weeds, ect....
You'll need a variety of equipment. There is a surprisingly wide array of conditions that require specialized equipment. Once you start adding equipment, you need to find enough work to keep it all busy.
I'm up to 34 full time employees, and 12 tractor/mowers for the upcoming season. The lions share of roadway mowing will require ground crews w/string trimmers, as well as trash clean-up detail BEFORE mowing.
I won't try to kid you, the return is quite good. I wouldn't be doing this unless it was. But the start-up cost is incredible. (I had a rather large windfall that needed to be invested when I was first getting rolling)
Long story short, there's money to be made, but the "fun part" (riding around on a tractor) is but a minute part of the plan. Mostly, it's just "business as usual", dealing with red tape and risk.