If you need a computer, then you need two computers.

No, this has nothing to do with making backups. You will have to make backups of the data on both computers.

It has nothing to do with networking. You may decide to network the two computers, as your needs determine.

It has nothing to do with the operating system or the software used. You'll need the full range of important software on both computers.

It isn't because two people may need to use the computer at the same time. You can decide whether you need a computer for each user.

So why have duplication, an extra expense, and extra work space?

The answer is rather clear.

Your computer will break. You can never predict when or under which circumstances.

If a backup computer is available, then you can switch to it when the need arises. You will be amazed how often it is used. This is a common situation with people who need a computer because they use it a great deal.

The price of computers has plummetted. You don't have to tolerate problems. Go out and get yourself another computer.

It is not really a luxury. When you're working you want to be able to do your work. You don't want to have to let the computer control you.

Having two computers means that you are in control. You can concentrate on your work and not wait for a broken computer to be repaired.

Even limited down time is frustrating. It's not worth it.

How can you afford this luxury?

Simple.

Computers are no longer expensive. A bottom-of-the-line computer costs less than the software that you would put on the computer - unless you plan to use open source software.

That open source software, by the way, may be a good solution for cutting back on the costs of your computer. It costs very little and it is usually compatible with the expensive software that you use on a regular basis.

Granted, there are differences between open source and commercial software. There is also the issue of a learning curve before you can actually use the alternative software. However, that is the price that you pay for using free software.