When we invest our money, how can we be confident that we can gain profits?
wow that's a pretty vague question...
first of all, you can't. you just can't. there simply is no such thing as a 100% safe investment, it's more about evaluating and managing risk. when you start to gain experience, you will have a feel for how risky an investment is. along the way, you will probably screw up a few times and learn some painful lessons, but that will help you better evaluate the risks involved next time.
Risk and reward are tightly linked. The higher the risk, the higher the "potential" for reward, which also means the higher the potential for loss.
If you want a super safe investment, put your money in your local savings account. Risk is super low, so reward is as well (usually at 0.25% in this market).
Do your homework. Buy the right property at the right price. Do not make any mistakes. Find the perfect tenants.