Hi there! I was recently thinking about starting my own PC building company/business, I am very experienced in the building community and I would like to get paid for my efforts. Here is what PC I have come up with to start, it's a budget PC and would cost the user around £350-400.
This questions been asked to death, but there is pretty much no money to be made doing this. The money is in support. Just think about how long it's going to take to order parts, build it, install and update the OS, market it, then divide that tiny profit by the hours of your time.
Then realize most people won't pay that, because they can get a prebuilt with a warranty cheaper. And that there are a TON of legal issues to deal with (sales tax, tax licenses, business licenses, liability, warranty, what happens when your PC blows up and burns sometimes house down and they sure you etc) Building PCs only makes sense to do for people you know. It's not just slapping parts together (and you couldn't make money even if it was), you're talking a business which is a whole different complicated legal issue on it's own.
is this a sideline or something you want to make a living out of? consider making more 'interesting' machines, i'm thinking mini-itx running off a power brick (i've built one the size of a hardback book), or custom AIO's. in that way you are not competing with pcworld, or scan/ebuyer etc. and you are different, and building something that people may not be able to get themselves, and certainly can't buy off the shelf. http://linitx.com/ ignore their mobo's and cpu's all out of date, but many case and psu options.