Google "netherlands youth hostels", they have a chain with several, but I can't recall the name of it just now. I don't know if there's one specifically in Eindhoven, though. If you can't find anything there, try googling "Eindhoven guest houses", sometimes they are cheaper than hotels, if more pricey than hostels. If all that fails, check a map and see if you can find something in a smaller town in the surrounding area. It seems that most villages have some sort of guest house, and generally they are pretty cheap. If you find one on a train route, you'll still be able to get into town easily, with the bonus look at small town life and friendly hosts.