1) Do you want to learn how to do most of this stuff yourself?
2) Are you mechanically inclined?
3) What are you waiting for?
I assume you answer "Yes" to 1 & 2.
I'm a huge advocate of finding the parts and getting everything together yourself. First step is deciding what you want, then learning what you are looking for to do that, and finally discovering how to find it. Then you build it! This is probably the most economical solution - though not always. We'll help you all the way.
Buying a built motor from a reputable source is not a bad idea, but being able to get help to solve problems that always come up might not be so easy. It just takes a lot of the fun and satisfaction out of scrounging your parts, and the ultimate satisfaction of firing that sucker up the first time.
Last, but certainly not least: Build that first one mild - save yourself a lot of money and grief.
