There are multiple reasons as to why the Devil would consider Tom Walker a good prospect for selling his soul (as told in Washington Irving's short story "The Devil and Tom Walker").
First, Tom is characterized as a man who "had a wife as miserly as himself; they were so miserly that they even conspired to cheat each other." Therefore, the fact that Tom p;laces money on a pedestal was a good clue to the Devil that Tom would be likely to do anything to have money.
Second, Tom and his wife had "many and fierce were the conflicts that took place about what ought to have been common property." Therefore, like the first quote explains, money meant everything to Tom. Again, this details the fact that Tom would do anything for wealth.
Third, Tom was in a very bad place with his overbearing wife.
Her voice was often heard in wordy warfare with her husband; and his face sometimes showed signs that their conflicts were not confined to words.
What this refers to is the fact that Tom was beaten by his wife. Tom, like many who are abused, would do anything to get themselves out of a predicament like the one he is in.
Perhaps the most poignant evidence which would have declared Tom as a man willing to sell his soul would be the fact that Tom "was not a man to stick at trifles where money was in view." This means that, for Tom, money was the cure-all to his problems. He readily agreed to the Devil's deal without considering the repercussions of the bargain.