Sell unwanted ones at the Castle Shop. Note that you'll only get about 10% of what you paid for it, and the transaction cannot be reversed, so choose the one you want to get rid of carefully.
To get rid of one of the houses you have you first have to empty it...and there is a button you can click to remove everything in one click. Though I am not sure where it is. Then you can go to and shop and click on sell and you should be able to sell your house. There is a limit on houses you can have which is 3 unless you purchase the epic bundle and then it has a potion that allows you to have 4 house. I hope this helps.
