This is all a straightforward math equation.

Second, @Lisa Marie your thorough understanding of your husband's math is commendable.

gotta just do the maths, are both of these loans on the same property?

Multi unit changed the math for me in some calculations.One exception to the rule above is syndicating with a PM who also is an LP and receives management fees as a percentage of profits (rather than typical PM fees).

Then another 20% down on ~2M for construction.The interest that we would pay is where I think my math gets sketchy.

It all depends how one investment capital availability and how one ability to see the market ….when I started I also started from mere 20k , but thru further deep dive and how much is my DTI I can do lot way better in my backyard than OOS, it is all in math.

The math said we’d easily make $150k/yr and more wouldn’t add to our happiness.

All the best BTW 99.999% of accountants can handle it, it's simple math. 

However, my math leaves me a bit short in terms of $$$... $375k * 0.75% (max LTV) =  $281k - $218k (current mortgage) - $15k closing costs (est 4%) = $48k.

With current rates my mortgage would be about 4600$ and doing basic math i would have to pay about 1300$ to live in one unit.