This quote from "The Devil and Tom Walker" reveals a number of details about Tom's character. Firstly, the fact that Tom has a "vast" house shows that he is materialistic and keen to show off his wealth to other people. This idea is further reinforced by the word "ostentatious," meaning that the house is designed to be showy and to impress others. Tom clearly cares a lot about what other people think of him.
The fact that he leaves his house "unfinished" and "unfurnished," however, suggests that he is a very miserly person who does not really want to spend any money. This is also shown by the word "parsimony," meaning an unwillingness to spend money.
So, while Tom wants people to think that he has lots of money and is very successful, he doesn't actually care about the condition inside. For Tom, outward appearances are all that matter, suggesting that Tom craves approval from others.