This deal was done with a conventional loan with 25% down.

Our bank will allow us to keep the best loan.  

A few years ago, we purchased a 5 acre piece of land that already has a foundation and septic, hoping to eventually obtain a construction loan and build a home.

Then when it is complete, have property appraised and refinanced to pay back the hard loan from my Mother or other lender and because I overfunded, receive cashback at closing and either pay back into the new loan or wait for another deal once I get renter in on this place with me.My hiccups will be my income to qualify for the new loan, and the fact that I have an existing mortgage which affects my DTI right out the gate.

I've applied for a conventional loan: 3 units, owner occupied, NJ, 5% down.I have enough W2 income to cover the loan and additionally, there are two units rented already. 

Looking into cash-out refinancing and DSCR loans and all of that but I'm getting ahead of myself as I don't even have the 1 yet lol.Nobody in my family has any experience with this sort of thing so I'm just hoping someone can give me their opinion on if this investment makes sense.The home is currently being rented for 2900 total (all tenants are month to month and have been there about a year each) and my monthly costs would be 1,200 included taxes, insurance, mortgage etc.I am considering putting the home on section 8 because the fair market rent would make my monthly rent 4k+ but I'm weighing the pros and cons on that avenue.From what I understand the biggest costs to me as a home owner would be a new roof or fixing the pipes for any reason..

I know that going on the loan in my own name would allow me to put more loans under my belt in the future before we get married and become one unit. 

However, you're referring to Fannie Mae's 5% down loan program for OWNER OCCUPIED 2-4 unit properties.

If not - you are bringing cash to closing just to get out of the loans you already have.

So, the seller gets the benefit of charging you a higher interest rate for a loan they did not originate.