Received 100k Capital for Investment how do I do this?

[Vincent Ng]

I was fortunate to have been acquainted with an investor who has took some faith in me. Giving me 100k to invest with. What is the best way to invest this money, I'm looking for long-term positive monthly cash flow. 

One option of looking at a property was this..

Cost: ~670k, 4 unit Multifamily

Downpayment: 135k$, financed by 100k from investor, 30k from me. 

Monthly Mortgage at 20% Down 4.2% interest rate included taxes and fees = ~$3,000

Rental Income = $4,000

Therefore, yearly rent income towards principal is 48,000 a year,

Can someone please explain if this is a good ROI?