Once you're behind on that, you need to build a bigger cushion than what you got real estate investing.

The buyer had someone else pay more to build it than the value added, they had someone else do the associated work, they can get home purchase financing, they do not need to wait months for the ADU to be constructed.  

@Garrett Mathis PMC software is mostly focused on tracking leases, tenant payments and then various other building data.

Start building a list of local  lenders (private and traditional)  contractors, handymen, realtors, wholesalers,  syndicators,..... 

Build your design around the area.You wouldn't want to do a Miami beach theme at a high mountain cabin.

The interest paid on a HELOC may be deductible if you used the funds to "buy, build, or substantially improve" the first home. 

Multiple factors influenced our decision but seems like it’s going to be our best move for the family and financially.

I am building a downstairs 1 bed 1 bath unit that will not have yard, bbq, hot tub, fire pit or anything else for outside amenities.

Leverage equity in other properties, build a team, and connect with local Houston investors.Good luck!

He will finance building the house.