For example im guessing i would start low down by selling pc builds on ebay, but where does one get the components at a low enough price to make a profit?[/quote]
That my friend is the billion dollar question.
Without getting too carried away or in depth here, if you think you can assemble PC's with new parts and just put them on Ebay, or advertise anywhere for that matter, and sell them for an actual profit, you are getting into one of the most widespread super-competitive markets on the planet. Trying to target the high-end performance PC enthusiast is by far even tougher. Much more expense in overhead to purchase only high end parts selling to the smallest segment of the PC market.
Most people who would have a high end PC would rather build themselves.
In order to purchase directly from a manufacturer, say Intel for instance, you would first need a resale tax exempt certificate (so you don't have to pay taxes on items you purchase intended for resale) you need a business license for city you live in, you need a federal tax ID number, and, here is the most important thing
-you have to be able to buy parts in large lots, CPU's for instance start in lots of 1000. If you can't afford to be able to buy in large quantity, you will pay pretty much what everybody else does, which means the only value of your prebuilt system is that you have already built it.
Now, for that to be of any real value to a buyer, you have to back it with some kind of a warranty. Do you have the resources to replace bad motherboards, CPU's video cards, etc. at your expense while waiting on returns or reimbursements from the manufacturer? Spending all day on the phone with people troubleshooting?
Of course then there is the whole accounting issue and sending Uncle Sam his share of your profits. You DO have to pay taxes on your profits