We have one of those carpeted multi-level cat play centers. If you have the materials, the time and are crafty, I say go for it. You would save a ton of money because most that size can run between $80 and $200. Just make sure you secure the levels really well to prevent hem from toppling over. Also, make sure you secure the carpet so they aren't temped to chew it up and shred it. My cats have a carpet fetish and will turn loose carpet into a snack if given the opportunity.
If you end up making one, please post pictures. I would love to see how they turn out. 4951