In short no.
Can you get the prices Dell, HP, ect.......... get, no.
Are you going to offer a 1-3 year warranty like Dell, HP, ect..... and full support? If you buy the cheap OEM version of Windows you have to offer support for it according to the license.
The lowed market is impossible to compete with Dell, HP, ect...... The high end market consists of a lot of do it yourselfers.
Most people are buying Laptops and Tablets currently.
Go look on Ebay and do a search for custom computers, and search completed listings. There are hardly any that sold. The ones that are selling are generally loaded with pirated software, and that can get you thrown in jail.
If you were to sell on ebay, a decent rig would end up costing you $100 at least in fees and shipping, majorly cutting into your profit since you have to stay competitive with everyone else.
It is a tough market, get a job and call it a day.