This is not valid housing. What is valid housing? [duplicate]

I built myself a decent sized house with a basement and it said it wasn't valid housing. So I built another one that is a very simple room with walls (dirt walls on the background, wood "walls") a door, two doors, a table, a chair, floors and light sources. I've gone over and over it and made sure there are dirt walls everywhere. It still says it's invalid housing.

I'm playing on Xbox 360.

I think your problem is this (based on you saying it has a basement):

If you dig into the ground at ALL and attempt to use the dirt wall as part of your wall, Terraria thinks it's not valid housing.

Take out that hammer and get rid of 100% dirt walls and replace it with whatever kind of wall you want.

Terraria Wikia has a complete list of everything required to make something valid housing. Light source appears to be missing from your description in the question, I'd start there.