If a team was at +140, that means you only have to riskR$1 to winR$1.40 orR$100 to winR$140. The key thing to keep in mind is that the payouts are constant regardless of how much you bet. To figure out the exact amount of risk/return, just divide the moneyline by 100.
Money line bets can be a great option, and their popularity reflects that. They can be more appealing than betting on spreads when you are picking a favorite because it doesn't matter how much that team wins by. And they can pay out a lot more than a spread bet if you feel good about an underdog winning outright.