This probably won't sound very useful for a 17 year old that's strapped for cash right now, but the fact that you're asking these questions right now is very good for the 20-something version of yourself.

Most people my age (ie anyone working full time) would kill for the huge amount of free time that 17 year-olds have. Use it to be spongelike - learn as many new languages, techniques, skills etc as you can. A great way to do this is with internships, or taking grunt-like jobs in places where you're surrounded by knowledgable people. By the time you're out of school (or whatever you're doing right now), you'll be vastly more employable than 90% of your peers.

But, in the short term... I made money at that age by designing themes for CMSs and cold-calling local businesses and asking if they wanted websites.

Good luck!