well as were now onto our past my first pc was an amd 160 mhz self built by myself. my god that was a long time ago. anyway i bought it for doom and others but like others, it was mostly for the games. the only thing i don't miss about those days is the working in dos (himem etc. *shudder*)
anyway back on topic - building or repairing pc's can be profitable but your most important part will be building a client base and getting customers via word of mouth so once you have enough skill to build a machine get out there and use it and don't overcharge initially - word of moth about your good pricing will get you more buisness, then you can start charging more for each job.