Price really depends on the shard and the facet, and then the location...the closer you get to a moongate typically on any shard/facet, the price goes up accordingly. I suggest you go to the shard trade forum where you plan to buy for pricing. I would also suggest using the forum search feature on your chosen shard's trade forum looking for housing sales to get a more objective view of the market.
I personally don't know of any scams involving housing...if someone transfers a house to you it is done via a secure trade window, and you each have to confirm your side of the deal (for example after you place checks for the purchase price in the window, and the deed is on the seller's side of the window, when you both check your side to confirm the deal, it goes through). It is pretty straightforward. All the access is supposed to clear automatically I think after the transfer, but I'd go into the menu and verify that all access lists have been purged after receiving possession, just to make sure.
-Skylark