I find old broken guitars at yardsales and fleamarkets for very cheap prices. Sometimes a broken guitar will go for $10. You can harvest a surprising amount of hardware from a demolished guitar. Tuning pegs alone go for $50 or more if you have to buy them new.
Making guitars involves design, woodworking, and music, which are my three favorite hobbies all rolled into one. Here are some guitars I've made.
I call this one "The Shovel" because of it's shape. The back was pieced together with 6 ribs. I couldn't find a bridge or tailpiece which would look right with this shape, so I found some walnut and carved this one.
This one doesn't have a name. It's very small and portable. I wanted it to be as thin as possible and still have an accoustic body. The hollow body is only 1" thick. The sound hole is shaped like a scarab (AKA dung beetle.) Depending on who I'm talking with, I decide which insect name to use. People 13 years and younger appreciate dung beetles more than the 40 and over crowd.
Here is my gourdtar. The sound holes are shaped like dollar signs. It seemed funny since it was a gourd. The dollar signs are vaguely styled after the f-shaped sound-holes in violins.
I wanted this one to be as stick-like as I could make it. the volume and tone knobs are on the bottom edge. I don't play this one very much. Turns out a stick-shaped guitar is very difficult to hold.
This one was ergonomically carved to be more comfortable to hold. It fits my belly better. A lot of times, guitars have frets way up near the sound hole, and then there's a body in the way so it's extremely difficult get to them. I put a deep scallop in this one so the frets are very easy to reach.