I have just ordered RPs for my twin daughters 16th birthday. I haven't a clue what monitors to get - I assumed I could get cheap 2nd hand monitors but the local shop has said that these wouldn't be HDMI and I need new - can't afford over £100 each. Help please - remembering my user name!
Just to add to James comments.
Do you already have a PC? Look at the back of the monitor to see what connectors you have (Wikipedia helps here). You may have VGA, these are 15 pins in three rows of five. You need an expensive adapter for these. You may have DVI-D which have more pins usually arranged in blocks and some of different dimensions. As James says you can use these with a cheap adapter. When you are satisfied you have it working look for a secondhand monitor with the the same DVI-D socket.
If your television has HDMI it is usually helpfully labelled HDMI as TV users are not expected to work it out for themselves. They have been around for a while so you might be able to pick up a secondhand one from someone who is upgrading.