What is Tom's motive?
After Tom met "Old Scratch" in the forest, he is offered a deal in which the fortunes that had been buried by Kidd the pirate would be his if he agreed to what the"devil" asked him. Those details are never told in the story, but it must have been serious, such as the sacrifice of Tom's soul, because Tom needed some time to think about it. However,
"....he(Tom) was not a man to stick to trifles when money was in view." ( paragraph 22)
However, when his wife found out about the conversation he had with the devil, her "avarice", or greediness, took over and she encouraged him to take the deal. Tom decided that if he was going to sell his soul to the devil, he wasn't going to do it because his wife wanted it. When he didn't respond, she set off herself to find Old Scratch and get the fortune for herself. All that was found of her is a heart and a liver. Tom then went in search for Old Scratch himself. It took a while but,
".....delay had whetted Tom's eagerness to the quick, and prepared him to agree to any thing rather than not gain the promised treasure..." (paragraph 37)
When Tom meets Old Scratch, there is one condition that the devil insists Tom meet: the business he goes into must
"....be employed in his(the devil's) service" ( paragraph 38)
Tom would not agree to the business of slavery, but he did agree to being a usurer, a money lender. The devil told him,
"You shall extort bonds, foreclose mortgages, drive the merchant into bankruptcy." ( paragraph 45)
Tom agreed to this and was quite happy until nearing the end of his life. So, his motive was greed. He wanted to be a successful businessman, a friend of the needy, and VERY RICH. However, at the end of his life, he became fearful that the devil would want his due.