You don't need much at all as long as you have a fully paid flat, kids and meet your

CPF min sum.

If you meet the min sum at 55, and if both husband n wife working now, they will each get $1200 from

CPF life. So you get $2400 pm.

You can rent out two spare room for $1000 per room. You get $2000 pm.

Your 2 kids give you both $1000 in total pm.

So, combined passive income is $5400 pm. This is a lot for a retired couple.

All this is possible if:

1. You both meet

CPF life min sum.

2. We have many FTs to rent our spare rooms.

3. You have 2 good kids to give you allowance.

This is the secret for happy retirement.