You could also try discussing with your boss to see if you can work from home. I did and now I work from home once a week. It's better than nothing.
Otherwise, you can look for freelance work which you can do at home so you can also keep an eye on the children.
If you can't leave your full time job for the pay and its benefits, then there's really no two ways about it. Raising 3 kids in Singapore is indeed expensive.
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