In Europe we've used regulations. There's standardised ways to measure area of an apartment/house, and it has to be included in any ads and contract of sale/rent. If the actual area doesn't match what's in the ads/contract the landlord/seller will be in trouble. I saw a news article once where the landlord,iirc, had to return all rent money to the tenant. The tenant had lived there for a while(memory is fuzzy, I think it was years, but don't quote me on that) and in the end only paid for electricity.

I hear you guys like suing eachother in the states, seems like this kind of regulation would suit you just fine!