You can start in your garage which is how Steve Jobs, Bill Gates, and Michael Dell started... well... Dell started in his dorm room but, it's not all that different :)

Yes, there is lots of money in it... but, like the other poster said, what are you offering that's different? Okay, so you can build a computer, but most of the people who need those services, are technically knowledgeable where they can also build the computer.

So, I think you should sit down and think about more about your idea. Who is your target market? Are you trying to market for the masses? If so, how are you going to appeal to the masses? Or, is your target someone more specific? Is it a young kid who doesn't know as much but needs a gaming computer? Are you going to allow this kid to pick out all the specific parts and then you guarantee to put them together (please say no to this because this would be impossible given that there are many components that are not compatible generally because of software issues). Or, is your target market going to be businesses who need specialized help?

Hope this helps a bit :)

~~~~~~~~~~~~~~