Unfortunately, if he wants to earn money fast, usually the sh*ttiest jobs pay the best money.

If he's in good shape, he could look into construction, general labour, etc.

If he's got a great personality, he could probably do pretty well at bartending/waitering/etc.

Government jobs often pay well, too. I worked a summer doing travelling surveys all over the state. It was a cush job and if I'd stuck with it (I ended up getting sick halfway through the summer) I would have taken home upwards of $15k for 12 weeks of work and 3 day weekends.