It can be profitable but the margins are small and the risk is great if you don't get sufficient collateral. How can the other party pay first though if you're the one lending the money? Do you mean send collat first? Most people wont trust you yet to send collateral first so you'll need to use escrow. Personally I'd avoid getting into the lending business as it's likely not worth the hassle and one scam is all it takes to ruin your total profit.