Owning a computer does not have to be as expensive as you might imagine.
There are reconditioned and refurbished computers, both desktops and laptops that are suitable, especially as a first computer, and these can be quite reasonable in price.
Software is the next big expense, especially if you decide on MS Office for example. There is a free Open Source alternative, Open Office. This is a multi-program package, similiar to Office and documents can be exchanged between the two.
Anti-Virus programs are very necessary and many are free. AVG, Microsoft Security Essentials are but two that come to mind. Make sure you download MSE from the Microsoft site for your operating system as there is a ripoff firm that infects your computer with a very similar looking package that they then contact you and offer to clean your machine, for a price (£120-ish)..
Anti-Malware such as Malwarebytes is another good defense against the attackers out there. Available as both a free and paid for service.
Adobe offer free versions of some of their software such as Acrobat Reader, which allows you to view Adobe PDF's, Flash Player, again allows you to view Flash presentations on the Internet for free and Shockwave, also for online presentations.