What’s the best investment for a low-income family (earning $1,500 per month)?

I think most important is to learn how to increase yr active income as priority.
If u want to invest, best to go for something safe like saving bond. Its more like saving rather than investment but it's capital guarantee.

I'm going to give a contrarian answer here: The best investment is in yourself. There is only so much you can gain, investing $100/mth into something like robo advisors (not that you shouldn't, but hear me ou first).

If however, you find a way to raise your value, skill set and human capital, then you can perhaps raise your salary to $2K/mth or even more, which will then be far more beneficial than trying to save an extra $100/mth to invest.

Ceteris Paribus, a person earning $2000/mth in a higher value job, after upgrading himself/herself, will have 33% more disposable income which, at this level of income, is more meaningful than hoping for a $100/mth pay raise to $1600/mth.

You can try Robo advisors with no min amount to start with (Stashaway), Singapore savings bonds or fixed deposits

All investment yields only non-guaranteed returns. As a result, it depends on the risk that you are willing to undertake in order to achieve your investment objective.

For this purpose, you may consider high rating bonds, or investment funds that primarily focuses on capital preservation.

Having mentioned that, do your own research to ensure that the tool fulfils your investment objective and risk appetite.

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