We got a GREAT deal on ours. A local toy store was going out of business & I asked about buying the floor model. I got it for $50!!! It's a huge Plan Toys house & came fully furnished (every room, plus animals, outdoor toys, garden set, etc). Everything was glued down, but I pulled it all up easily. So, keep your eyes peeled for something like that.
Also, Micheals Crafts has some wooden dollhouse furniture that are literally $.50 to $2.00!!!! Chests, armoirs, etc. I think AC Moore Crafts also has some.
Also, sometimes on ebay you can find some.
Good luck!