I'm from Northwest FL, I'm 19 and been in this industry for 2 years, in college full time and am running my own lawn care company full time with about 25 customers. I don't really enjoy it that much because it isn't what I want to do the rest of my life but I've learned tons about how business works.
Here's my 2 cents to any teenagers or anyone getting into this business. You don't ever lowball, and don't ever get a false sense of responsibility toward someone, their urgency isn't your emergency. Find out what the people do for a living before taking on their business so you have some security. Buy reliable equipment!!!!!!! I run a Gravely 44HD with 24hp Kawasaki, Echo weedeaters and edgers and blowers. Don't buy offbrand crap just because it's cheaper, your maintenance support will suck. Just a side note, when buying a riding mower, check the muffler mounts, if the muffler breaks, its not professional to run something as loud as a NASCAR in their yard.
If your a teenager, do not be overconfident and do not take business away from other landscaping guys, this is their livelihood, you probably still live with your parents.
GET AN ALLY, seriously, someone you can count on if you have any sort of extenuating circumstances. You trade favors with that person and don't screw that up.
Lets see here, don't be afraid to give prices, people know what stuff costs, and make sure you either have them mailing you checks or your collecting at the door, don't do any of this mess of calling and meeting up and all this other bull, you'll lose all your profit margin just hunting people down.
God Bless!! and Happy Mowing!!