Since you mentioned an interest in woodworking, I'd like to build on that idea a bit. Rather than going into it full-speed ahead (which I know you've mentioned you tend to do with stuff you set your mind to), maybe consider giving it a try without going completely equipment-heavy.
I'd suggest a table saw, power miter saw (preferably sliding for making larger cuts), a router and a set of cordless power tools. Because of my job, I'd say I can give you pretty accurate pricing. If you go mid-range on the pricing (stuff that's made to hold up, but not necessarily construction-grade), this is about what you could expect:
Table saw, $300. (Could get by with $200 but you're giving up a lot of quality and portability.) Miter saw, $200. Router, $150. Cordless tool set, $160-$260 depending on battery type you decide on. The saws would come with decent enough blades that you could get away with doing most types of cuts with them. The router would require you to buy a bit set, decent sized assortments (though fairly cheap quality) would run you $40-70. And of course, the drill in the cordless tool set would need a drill/driver bit set, which you could pick up a decent starter set for $20-25. (For reference, all the tool prices I gave you are Porter-Cable tools.)
So that would put you at roughly $1,000, assuming you bought everything brand new. (I wouldn't be against the idea of buying the saws used, maybe even the router if you're sure all the parts are there, but I'd be very wary of buying used cordless tools, since you have no idea how much life is left in the batteries and new batteries can pretty much ruin any savings you manage by getting the set used.)
As for materials, don't underestimate plain old pine. It's actually become one of the more desirable craft materials lately (from buyers, not sellers). A lot of people are into stuff like the "rustic" look right now, and most of that stuff involves pine. It's also much easier to carve out than a hardwood like oak or poplar.
If you were selling your stuff at a booth at a flea market or a craft mall, you wouldn't even have to outright advertise what it's made of, and just save it for the people who ask. Most people won't even care what it's made out of as long as it has a nice stain/paint/finish job, unless they're woodworkers of some sort themselves.
As for making the money to buy the tools (since I get the impression you're on a tight budget), you could even start small. I never did any major finish-work on my son's bed (people here are into unfinished pine, go figure). All the materials I used to make it cost me about $50, and that included buying a couple bits I was missing (and I had some extra stuff when I was done). I borrowed a small miter saw and electric drill from my dad. So, a $50 investment, and with a bit more attention to detail and possibly a nice stain job (another $10, which would be enough to do 4-5 beds, probably), I could have easily turned around and sold the thing for $100+. All in the course of a few hours (because I only had an idea of what I wanted to do, and I didn't have a template pre-made).
If you'd rather not go that route to make the start-up money... Back to the garden thing. Let's assume you use everything you currently grow in your garden. Without taking up a TON of extra space and keeping the cost minimal, let's say you expand your garden size by 10%. That 10% of extra vegetables can now be sold (for whatever people pay... I'm not a veggie person so I have no idea! ; ; ). You take that money, put it into a savings account or even just an envelope under your mattress. That money will build up all on its own, assuming the stuff sells, and after you've bought the seeds the first time, the stuff reproduces pretty much on its own, so you have an even smaller cost from here on out.
And... That's about all I've got. /soapbox OFF
For what it's worth, here's how my son's bed turned out: