I aint a teen but I will mow your lawn for $10 as long as you buy the gas. 
One kid in the 'hood ( parents separated ) passed out an ad to mow lawns. His price was
way too low. Of course one of the neighbors with a weed patch which should only be done with a side bar mower immediately took him up on his low ball price (This would be the good liberal vegan btw) bagged and rememoved no less. To the kids credit he did the job. What a compasionate soul taking advantage of a kid in time of need.
Mowing costs vary but you have to include things like gas and oil, blades and clean up bags in the equation. I don't think the kid covered his fixed cost on that job let alone got anything for his time.
I have about a half acre which takes me a couple hours to do with a small yard tractor
or a 20" push mower. (With the tractor you have to do more trimming than with the push mower only , I am a fussy SOB there are lawn plantings and gardens to contend with). Sometimes I use the mower only other times the mower and tractor, depends on how I feel and how hot it is. I figure it would be worth about four times what the kid was charging the neighbor, a lawn service would probably charge eight times as much and run over shrubs.
Ten years ago I had a company called TrueGreen doing the fertilizer. After several years I dumped them when they had the nerve to asked me if I want their crabgrass treatment. Told them no, I had enough thank you, they didn't need to give me anymore. (I had been paying for crabgrass control and it kept getting worse because they didn't put it down at the right time or at all who knows) It took two years to get things back under control. Hank Hill got nothin on me when it comes to a green weed free lawn now.