Only risk really, if you're getting mortgage to get apartment to rent is that prices go up but you can then just increase the rent. Aside from "tenant completely trashed my house", the risks are nonexistent, it's one of safest ways to invest your money.
Similarly, value decline is another real risk. I have lost 200k in value on home I live in. If I needed to sell, I would be SOL, which is a low occurrence but serious risk.
Are you a landlord? If not, why not, if you are convinced the risks are nonexistent and it's one of safest ways to invest your money?
Reality is that while risk is moderately low (but far from nonexistent), returns are also very low, so being a landlord isn't a particularly good investment. You're much better off in the stock market, at least up to the point where you have so much money that you start needing to diversify.
Sounds like you should try it out, then.