When Dan Martell sold his start-up computer company in 2008, he became a millionaire at 28 – an age when most people's personal finances are barely taking off. It wasn't long before the money leeches caught wind of his new-found fortune. “A lot of people were approaching me and asking for money, especially on Facebook,” Mr. Martell says. The affable Moncton, N.B., native politely turned down the pesky requests. Instead, he splurged on a cottage, a boat and a hot tub, and spent the summer wakeboarding. But in the fall when his buddies went back to work or school, Mr. Martell found himself in a slump. “I went through ... (full story)