where is it gunna be based ?

Why would you post it here? How old are you? What do you intend to actually do? Can you pay? How much? Most importantly, where?

i am 15 i am starting a online store and local sales like craigslist i intend to build pc such as for gaming video and etc i also am ganna be making laptops and tablets soon to come i can update and make computers faster i know how to build computer and such as u can not tell and more info needed

u will make the half the money each computer or update or etc

It's not profitable enough. You also have to consider supporting all the systems you put out. with larger companies, it's much easier, but on a small scale, it's much more difficult. You also have to be able to get over the hump of the first few systems, and you will not always be in the black ink for the first builds, depending on your profit margin.

The people of Craigslist are not intelligent. They will need help, and they will ask for it. More time, and time is money.

Craigslist is no place to run a business.

We would have to be in the same locale, we are probably not. There's no benefit in grouping with other people for things like this. Building systems is a one-man job, even at larger-scale building companies.

The best thing to do is to try to sell a system you built for yourself. If you're in no hurry to have a system, see if you can profit by listing it on Craigslist for more than you paid for parts. Invest the profit in a new system, or build an identical system and keep the money. If you keep reinvesting until nobody buys, you could have a much better rig than the one you started with. Still, this requires a lot of work.