I am a huge advocate of repairing and building one's own bike...but, it can be frustrating due to the myriad different sizes of everything on a bike.
My son wanted to get into cycling, but wanted simple. No gears, but wasn't sure if he wanted to go fixie with his first bike. He also wanted to pay for it himself. Enter SE Draft light. Bottom of the line single speed/fixie flip-flop hub deal. Steel and durable. Got it super cheap on Ebay around $200.00. Started riding it, and figured out what he wanted to upgrade. Switched out a few parts and rides it more. He is learning how to work on it himself and by riding it he is figuring out what parts he likes.
Eventually he will replace the frame and wheels, but he started out riding a new bike, and has gained a ton of mechanical experience in the process.
Oh, and part of the reason sonny boy went with the SE brand is loyalty... dear old dad rode for them waayyyy back in the day.