I worked for a guy who startred his own company building PCs. It was him, the PC tech, and a part time teacher for their classes. I came in as a 2nd tech & do-everything guy, but now work at a Hospital mainframe room. He does very well actually, has some large accounts with some of the local buisnesses & colleges.
If you do quality buisiness, do quality work, use quality components and then have quality support, then you will do well. Word of mouth is great advertising. User would call in with a problem and if it was under warranty, they could either bring it right in, or we'd go right out to their house and fix it. I built most of their computers when I was there and they were all put together well, everything mounted properly, cables out of the way & organized.
The main service tech was the kinda guy that would explain everything to people who walked in. They would leave knowing a LOT more about what they want & need in a computer, not plain "hype" like at Best Buy, CompUSA, etc... Most people walked out of our store as happy customers with a new computer, and most were return customers as well. He would show them how these kind of computers were completely upgradeable, unlike the name brands. A lot of our buisness was servicing these name brands as well,
We would have various setups, lower end & cheaper general user PCs, mid range, and ended up showing a gaming PC (me and the main tech started a local gaming club

). Loaded them with all the software the user would get, and they could come in and mess with them while we explained everything about them. It also sounds a lot more honest when you actually KNOW what you're talking about, and can get into detail.
Our PC classes and computer camps for kids were popular too. The kids got to play with the robotic legos and could program them to do stuff. Even got into hosting classes at a local college.
Our prices were pretty comparable(esp for the components we used), but our support beat them all. Not bad for 4 people(2 full timers & 2 part timers).
It's quite possible to start your own company and make it a success, which is usually HONEST friendlyness and great support.