I’m looking for a 2 family home, budget is 350-375k max, and in my area (Hudson, Bergen, Union and Passaic counties in NJ) that has been quite the challenge.

If you feel you can make a strong case, then I would challenge the appraisal.

Your bigger challenge could be taking title in the LLC for the new purchase, unless working with a local bank who will allow it - like Firstbank.

I'm 35, engaged, and have a 9 month old baby girl at home. 

Everything will have challenges, which challenges do you want?

This is one of the big challenges with small multifamily properties.

Developing that trust with someone you don't know may seem like a challenge, but if you approach it correctly, you should be able to achieve a pretty solid foundation of trust. 

I already got a property manager engaged and he advised that I could rent the house for $1,800. 

Erdek from that other thread should be followed; don't give a private loan without engaging an attorney like John who is familiar with how to protect the lender.

Also,  have a discussion prior as to your involvement if you would like to be completely passive and simply receive quarterly updates on your investment progress, or if you would like to know the challenges and why specific decisions were made along the way... latter of course takes additional time commitment.