Depends on where you live. In Rockford IL the city subcontracts individuals to plow some of the narrow side streets. I'm sure other large cities might do the same thing.
Otherwise most individual plow owners do driveways for other people, and drives and parking lots for businesses. Often a group of guys will form a plowing business and line up a lot of places to plow.
Years ago, I drove for a guy that owned 7 plow trucks. Each truck had a designated driver and route. When you climbed into his truck, you were there for 24 hours to complete the route assigned to that truck! We were connected to each other by CB, and if you had any kind of problem someone was there in a few minutes. He had 2 backup trucks in case one broke down. He would buy everyone plowing breakfast, lunch, and supper, we would all meet and he would check to see how everything was going. The guy was a jerk as a person, but come plowing season, he wasn't a bad guy to work for if you didn't mind the hours. A single 3" snowfall was worth well over $10,000 to him, after expenses, and that was over 10 years ago.
The business is hard on the trucks, hard on people, you count fuel mileage by hours per tank full, and add a shovel man (or 2) for those places you can't get with a truck and a couple trucks with salt spreader that can dump a 50lbs bag in seconds, and you get an idea of the cost to do business. The going rate around here is $60-$75/ hour for the driver and the truck, the shovel guy, the salt spreader, and the salt are extra. Complex drives or ones requiring extra care are more expensive. If the driveways are close together and a simple push it off deal, a truck can do as many as 6 driveways an hour (though 4 is more realistic). $20-$25/ driveway is not out of line, more if more snow. 3" seems to be the standard.
A lot of guys that do landscaping and mowing in the summer do snow removal in the winter.
If your equipment isn't up to par, its hard to make money plowing snow. Most people contract plowing out their drive dependent on a certain amount of snowfall (like, plow if we get 2" of snow) and expect it done before they have to go to work in the morning. If your plow breaks, you might have to hire someone to do your contracted jobs. Gene