If you're old enough and your parents agree, you could mow lawns to earn some extra pocket money. After checking with your parents, the best way to get started is to ask your neighbours if you can mow their lawn for them. Mowing could be a once-off job if your neighbour is going on holidays or is too busy, or it could be a regular job you do for that neighbour.
It is important to ask your parents to show you how to use a lawn mower correctly and safely. Ensure you have all the proper protective gear before you start, like ear muffs, glasses, closed shoes, gloves and sun-protection.
If you're too young to mow the lawn, you could offer to help weed the garden or rake leaves to make some pocket money.