I just floated this idea by my wife this weekend but she shot me down based on not having the time to do it over the weekend due to commitments with the kids sports that are still in season, but it is easy money.
I pass at least 5 lawn care service crews every day, and their gear ranges from a beat up Ford Ranger with a garden tractor in the bed to decked out Ram 2500s with two zero turn mowers and 4 weedwhackers hanging on the sides. I also work with a sidejob family that mows locally, and yesterday they were mowing 10 yards total.
I'm assuming that every yard nets them $50, and with 10 yards that's $500 a day minus whatever gas you use for the job, which I'd guess can amount to $100/day. Still 400 a day is fine with me.
My plan was to mow 4 yards over a weekend for an easy $200 over a weekend, as we live next to a very affluent neighborhood, so I could cut my travel time and gas costs by staying local, but again, she didn't want me spending 4+ hours every weekend doing the work.
PS - if you choose to go this route, you WILL need to cut off all of your T-shirt sleeves. There must be a law around here in PA that all lawn care workers must have their sleeves chopped off to do the job.