How do I find a job at summer?

Its summer now, And I live in a building near the beach, there's nothing to do and We already tried every single summer camp. My brother and I, I'm 11, he is 9, tried helping out the neighbors by walking their dogs and stuff, and earn like 5$ an hour, 10$ 2 hours, like that. But my mum said we can find something better than walking dogs, I dont know what I should keep myself busy with, And we'd like to earn little money, just for us, because we're tired from asking our parents for money and they said that we can have a small summer job to learn about money and stuff. I need your help, what should we do? Dog walking has really backfired cause not many people want to give their dogs to strangers, so we dont know, and I already said we live in a building so we cant open a lemonade stand or whatever, so you got any ideas? Thanks