When I was too young to work I made a ton of money house/pet/plant sitting when people were out of town. It was so easy and only took a short amount of time.
I think it's awesome you are looking for ways to make your own money, rather then just ask for it like my kids would do. And Bats are your friends. Yes, they make a mess, but you take the bad with the good.
When I was in middle/high school I used to sell apples from our orchard, and maple syrup from our sap house in the spring. In summer I would mow lawns (using their mower). In the spring the local tobacco farms would start hiring for people to pick tobacco in the summer. I don't know if they do that anymore, but there was good money in that and their used to be a waiting list for summer jobs from the kids in high school. I also used to weed gardens, and do light painting. I lived in the hills in western massachusetts.
Now that I live in the 'burbs, I get flyers on my door from kids wanting to do everything from mow the lawn ($20 a pop are they serious?!?) to picking up dog poo in your yard. Picking up dog poo is a good deal $5 and they will clean up your yard and take it with them. And I *hate* dog poo. Hate it.