When you buy a new computer, you'll generally receive everything you need to go online immediately. You'll probably be advised to buy the biggest hard drive, the most memory, and the fastest processor and modem that you an afford, so your computer has enough capacity to work well now and in the future. For several hundred dollars, in contrast, you may be able to buy an older model used computer and a printer, and add a modem and communications software. This set up may be all your family needs to write letters and school reports, use e-mail, and browse the Web. Of course there will be tradeoffs in terms of speed and performance, and you may run a higher risk of equipment breakdown.
Some stores specialize in refurbishing used equipment, or inspecting it and replacing worn parts.
If you take this route, find out what parts are new before you buy and ask whether you can get a warranty. Also, with any used set up, make sure that any software that is included is licensed, rather than an illegal copy. Add upgrades over time .You can buy additions you want or need later and install the upgrades yourself as you learn more about working with computers.