Store (Shop) for selling computers and its peripherals?

I was just thinking of doing something for business. So what I thought would better was to put up a shop to sell computers and its peripherals. Now one has to furnish and do lots of thing to make the shop attractive and presentable to attract the people.

But about the items on the display.

Do you have to buy them or the company (manufacturers) give it on credit for reimbursement of the price as and when sold?

Or do you have to pay marginal price?

Is there any other system?.

Thanks in advance for your assistance.