I don't understand the question. A mortgage is borrowing money, it is not an investment. Buying a home is an investment, and often requires a mortgage if the buyer can't pay cash.
Do you want to invest in other people's mortgages? Where you lend out principal and get regular payments of interest? Or do you want to buy a home, and are thinking about getting a mortgage to help pay for the home? Could you afford to pay cash instead? (Because then we have to talk about other investments and opportunity cost.)
