Real Estate investment

A couple of my friends are taking loans from bank to buy an apartment in Bangalore. One of them is planning to take a home loan of Rs 2,000,000. He plans to live in a rented apatt and put his newly bought apartt on rent. So I believe he's taking the house as an investment.
The doubt I had in mind was if it was a better option than other forms of investments where he doesn't have to take loan and still could invest enough over a period of 20 yrs. Of course, the value of his apatt will increase with time. Still, I would be uncomfortable in such investments. I have no idea about how real estate works. Only time will tell how wise the investment is.