Yes, at this point you are going to see me as someone who cannot read instructions properly. But anyways, the subject says, How to sell a house? I'm not bragging about how the sell is so low, I just want to see the house see.
I'm not sure I understand the entire question. However, I *think* you want to buy a house to look around, then sell it? If that's the case, then you might want to Preview the house instead. For the Crown Shop houses, there should be a magnifying glass icon just below the picture, above the price and Purchase button. Click on that, and a very polite and enthusiastic cat lady will give you a tour of the house for free. (She'll only describe it once, but you can continue to visit and look around for free later if you still haven't made up your mind. You can't decorate it until you buy it though.)
I believe that the housing merchant in each world also has the option to Preview the houses they have for sale, although the button is in a slightly different place. Again, you can inspect the house as often as you like until you find the perfect one.
I really would not recommend buying a house just to look around - I think you can sell houses purchased with gold back to one of the housing merchant turtles, but you will get a very, very small amount of your money back.
