Help. How do I build a room in an apartment building?

Well, I tried to renovate the existing room but it wouldn't let me add anything OR delete OR edit anything like recoloring so I thought I'd just play it cool and pretend to have made changes when I hadn't and I thought I was going to pull that off but in the end the client wasn't that dumb. She wouldn't pay me for simply using her kitchen to make a meal, watch her big screen tv and take a nap and then call her back.