the name of movie where Tom Hanks buys a house that comes apart as he tries to move in?

The movie you're thinking of is "The Money Pit" (1986).

In the film, Tom Hanks plays Walter Fielding, a man who falls in love with a beautiful Victorian mansion and buys it despite the warnings of his girlfriend, Anna (Shelley Long). As he tries to move in, the house literally falls apart around him, leading to endless repairs and financial woes.