Have you tried agricultural labor? Picking fruit is pretty good because you can live in a tent all summer to keep cost of living down while making a bit of money. Depending what wages are like where you live it may even pay better than flipping burgers. Plus once you've done it you can use it to pad your resume really easily. Cherry season is probably just starting in the northern hemisphere and they really are the best thing to start on because they are light and pay well.