Plot hole: Walter and Anna each agree to pay half of the $200,000 for the house. However, Walter borrows the full amount of $200,000 from Benny. He also didn't know the house was a lemon.
Plot hole: The house has no pool, even though Walter tells the homeowner she has the best kept pool he's ever seen.
Suggested correction: When Walter tells the homeowner that the pool is well-kept, she lets out a groan that suggests that it's a flood.
I think it was because the lady who owned the house said her husband was deported out of the country because it turned out that during the war her husband was Hitler's pool boy, and she didn't know it. I would assume that he would keep a nice pool and since her husband was gone, she needed to sell the house.