I dont know much anout this althoug I had the same Idea. I think each desktop may need to run at the same resolution... althoug I cant vouch for that.
Theoretically it is possible.
Cheap mons available click here for under £250 althoug I am not sure on how good the quality will be as they will be basic.
The cheapest is 156 plus VAT. Spend closer to 200 and you will get a much better mon from the likes of CTX/Samsung....