I was lucky enough to be given 3 boxes of new carpet tiles from some offices that were being refurbed and were no longer needed. Easy to lay, and very hard wearing, when they get a bit grubby i give them a good sweep with a stiff yard brush then a vacuum and they come up a treat.
Sometimes being a tradesman is great, for my workshop i have been given by my customers, my carpet tiles, enough plasterboard to board the entire ceiling, an £80 length of worktop, some light fittings, a gallon of white paint and some shleving!