How to generate 40k passive income monthly in 20 years

[Sue Zikria]

Dear Forum,

What is the safest most effective way to earn 40k passive income monthly in 20 years by retirement?

I have 100k to invest now plus I save 2-3k monthly from salary.

I’ve been researching small MFH but not sure if that would generate enough passive income monthly in 20 years?

Also I live in NJ which has high real estate taxes.

I have an IRA but don't want to take money out of it for real estate investment.

Any feedback would be greatly appreciated.

Best regards,

Sue