^ Google it.....or call your county Agriculture extension (if there is one)...I'd guess you'd have to at least 18 to get a applicators license, so I wouldn't recommend pursuing that at this time. Maybe in a few years though. Things you could chase now would be mulch, power washing, aerating, general labor like painting fences or whatever.....You don't need any special certification for those types of things. Personally, Mowing is my bread & butter. My second largest revenue service is brush mowing (I have a tractor and bush hog to do this, not cheap to get in to), then it's probably a toss up between mulch/stone and power washing, I also do some light tree work. If a tree is down I'll come clean it up, I'm not an arborist though. If some odd job pops up and I know I can handle it and if I have time, I'll do that too.
I'd suggest staying away from tree work at your age, it's super dangerous and real easy to cause substantial damage to people and property. I also do fair in Winter time with snow service. You of course don't have a truck and plow, but shovels are cheap and easy to come by. Offer to wake up real early on snow days and go around your neighborhood shoveling drives and brushing off cars, maybe even warming up a few cars so the customer has a nice heated, cleaned of car to get into?? You could spend 30 or 40 bucks on a decent snow shovel and one of those foam snow brooms for cars. That's assuming you even get snow, not sure where you live.
FWIW, You didn't get the 600 for free, nothing is free. If your parents picked up the tab for it, make sure to repay them somehow. Do something for them that is at least equal to, or exceeds the price of the blower. Do some house chores like ALL of the yard work at home, do the dishes, sweep the floors, etc. You might already have this covered, just don't take a $600 piece of equipment for granted. Turn this in to an investment for your folks. They shell out the $ but get XYZ in return and more.