An "estate" can refer a piece of property, home, etc. However, in legal terms, an "estate" also refers to all of the property that a deceased person owned: money, real estate, art, stocks and bonds, etc. Dale's uncle didn't own the house, and the rest of the estate's value was in the art collection which went to Edna. Dale therefore would end up with very little.
It always bothered me that the uncle could afford to pay rent on that massive mansion, yet he allegedly had no money outside of his art collection. Where was the money coming from for rent? I guess it works for the purposes of the tv show.