The single-family home has gained $40,000 in equity and is expected to generate $600 to $1000 per month after renovations.

We do have over $250k in equity in the home though.

I’m a little lost on this as you could bring her in equity wise like the parents or on similar terms. 

It is sitting in equity.

Just because you have $100k in equity doesn't mean they will lend you $100k.

Forced Apperception (BRRRR or buying at a discount) allows me to build in equity from the beginning of the investment in case I need to fire sale the property for an unforeseeable reason.Debt-Paydown and Tax-Benefits are just a result of owning real estate and can be more-or-less predicted over a time period.

But moreover, it's unlikely you'll get any built-in equity.

I am open to other scenarios.We have access to $200k ish in equity in our primary.We will soon have access to another $100-150k for retirement/investing/IBC/etc.I would like to move into my young family into a (new build or fully renovated side by side) duplex.

So if your property is to appreciate only 5% a year, and you put 20% down on a $200k property, you would be earning $10,000 in equity every year NOT including loan pay down.

Single income (married with kids) and own primary house with $250k+ in equity.