I was thinking of, as summer employment, running basically a grocery courier/delivery service around where I live when I'm not in school (at school in northeast MA, live outside boston) -- but I don't know too much about how I might go about that, most notably, how much to charge for runs.
I do in-home care for the sick and elderly. I get paid 32 cents a mile for using my own wheels. That is in addition to the $10.50/hour base pay. You might also need to be bonded. A big source of customers would be the elderly. If there is a city or county agency that helps the sick and elderly look for work there. There has got to be a better paying job than delivering stuff by bike.