Every single great builder that we all look up to and read about in books, magazines, and here on the web had to take the big leap and build their first instrument at one point in their life. Some of those first instruments were nice, but I've also seen a lot of them that looked and sounded like a poor school project. Yet, with patience and perseverence, they were able to refine their skills into greatness.
If I told you that you'd likely spend 600 hours building your first bass ( or more) and spend a grand or two when it is all said and done, a lot of folks would back down, even though at the end of a year or so, you'd have an instrument to be proud of and you'd have learned an amazing amount. Why is it that those same people who backed away from it will, in the same year, have no problem spending five times that amount on fast food and will waste double that amount of time on the web and wind up with nothing to show from it?????
If you feel like building an instrument is something you'd like to give a try, DO IT!!!! I've heard about every negative response you can think of over the course of my life from people who were always telling me that I can't do it. Luckily, even at a young age, I didn't listen to any of those people. I cannot think of any other way that I'd like to spend the limited time that I have here. If you want to build a double bass, then build a double bass. Don't build a uke or a hurdy gurdy or a dulcimer or anything else that some folks will tell you will be easier. You'll wind up with a funny instrument that you don't know how to play and you won't be any closer to building your bass. I can tell you from experience: building 400+ sets of mandolin ribs will make you very good at building mandolin ribs, but then when you finally try to bend a set of bass ribs, you'll be back at the first day of school....
Have you read this thread?
http://www.talkbass.com/forum/showthread.php?t=547486&highlight=james+build
I built almost that entire instrument using just a few hand tools that would fit in a child's shoebox, and called on a few favors to cover the rest when needed.
Go for it, give it a try, don't be afraid, and get started now- not next week or next month or next year or some undefined day in the future. If you've only got $30, then start with a small blank of ebony- or 1/3 of that on a nice block of hard maple- and build your tailpiece and put it on your existing bass. Then when you get a few bucks more, move on to the next step....maybee get a nice board of maple for the ribs...and start working on your bass. Right now you are stranded on a desert island. That sailboat isn't just going to happen because you think about it a lot, and the whole process can be a bit overwhelming. Start with a tangible aspect and get the momentum rolling; great things happen this way.
Start right now by turning your computer off! If you sold your computer and cancelled your web service, you'd have enough change to buy almost all of the materials- nice materials, not bottom feeder stuff- and a few tools that you'll need to start building your bass...
j.