Bottom line it, no matter if it is Primary Residence, was a primary residence, or is rental, if you take out any type of HELOC or equity loan, and use the proceeds for reinvestment, you can deduct the interest on those loan at the reinvestment level, only to the extent you reinvest it. 

Once a house my brother and I co-own (inherited property in rough condition aka not getting rich off it) sells in Vermont, I will be debt-free and have some savings for a down payment.

I am looking at several buildable level lots for sale in the Los Angeles area, they have real streets not paper streets, they have houses most of the times on both sides... is it still a wise idea to build on a lot in L.A from scratch? 

The law is complex and depending on your income level may provide you with absolutely no benefit.

As a "sole proprietor" you end end up paying self-employment taxes because you're both an employer and employee.

you should do less buy/hold at 150K level.   

We have a 4-plex in commerce city, colorado (80022) that we purchased in 2015.

I always like to set a standard for the level I'm leaving while jumping up a level.

Those folks run a sophisticated operation, and if we don't keep up with their level of sophistication (and exceed their customer service) we would lose business to other investment classes that treat their investors better.Perhaps it could be said that the competitor to TK firms is buying homes directly, and that competition lacks sophistication--thus the hurdle is just above that level and anything above that is good enough. 

Using a buying agent for large purchases isnt normal practice since the listing firms are seeking dual agency and wont co-op commissions.