I totally agree with everyone who is suggesting rental income. You must have at least one flat [not apartment!] by the time you retire!
The immediate problem is, how do you raise the cash to build a flat - without over relying on loans?
Step 1: Identify a good location where you want to build the flat and buy yourself a plot there soonest - Prices will not wait for you.
Step 2: Identify areas which have not completely opened up but have great potential and get yourself huge pieces of land at bargain prices. The sale of this land in future will partially finance your construction - Capital gains.
Step 3: Invest in the NSE and other avenues. You will use the gains to finance construction in future.
Step 4: [Which is actually step 0] - Define "future". When do you want to have your first tenants. This will inform 1 - 3 above.
NB: Rental houses can be as passive as passive can be. There are some tenants who have never seen their landlord - ever! Get a reputable agent and they will manage everything for you professionally!
Approach Two: Zawadi 2929 - When it finally comes back - "bigger and better".
Never count on making a good sale. Have the purchase price be so attractive that even a mediocre sale gives good returns.