Where do college kids look for summer work?

I'm looking for some summer job resources my son can explore. He goes to college (rising sophomore) in another city but will be in Oakland for the summer, so he's trying to figure out how to approach looking for jobs remotely. If anyone has advice, websites to check out or specific companies/opportunities to recommend, I'd love to give him some places to start looking. He's open to pretty anything, thinking probably retail will have the most options, and would be extra happy if it involves bikes or engineering. Thanks!