I got into it about 6 years ago because I wanted custom guitars but I couldn't afford them. I spent probably a year or so before that reading everything I could on the subject and also on general woodworking techniques before I really felt prepared.
I had assembled parts guitars and worked on my own guitars for several years also, so I had a good knowledge of guitars before I ever thought about building from scratch. Once I had collected the tools and things I needed, I built several prototype guitars that I never fully set up to be playable, but only to practice my approach to building and my woodworking techniques. The first time I built a fully playable guitar it turned out great.
I have a background in engineering and 3D design which came into play heavily with my guitar building, so my experience may not be similar to many others'.
The cost per build will vary wildly. Take a stroll through a site like Stewart Macdonald and price all the hardware. You can easily spend $400 on hardware (including truss rod, fretwire, electronics, etc.) and a couple hundred more on wood. Several hundred more on wood if you go with some exotic pieces or highly figured woods.
The cost of tools and equipment will make the first few builds extremely uneconomical (to say the least) - but once you get past that things seem to change. If you have access to a nice woodworking shop from the start you'll have a huge advantage, some people get lucky that way - I didn't.
