Since HELOCs are variable rates my potential lender stated you can always refinance your HELOC into one payment by combining your first mortgage. 

I think Lowe's has a similar tool/service.I'm not sure how big your project portfolio is or your budget, but for a complete solution, Procore <https://www.procore.com/construction-os/core/> is pretty popular with the large contractors, but they offer a "variable pricing model".

Lots of variables, but it only works if you can launch the boat yourself, or if you have someone very trustworthy and knowledgeable who can do it.

The long distance part is doable, but its just another variable. 

There are just variables we can't know about your situation, so prices can vary widely.

Short answer: yes, it's possible.There are a lot of variables, of course.I'm assuming this us California.

Variable from now on especially if the goal is to BRRRRTriumph: only cost 3 months interest to break and refi.

So you're left with a variable rate commercial type loan with higher rates, adjustable rates after either 3/5/7/10 years, and a balloon payment (so you're forced to refi into higher rates at already incredibly thin margins). 

Plus an infusion of cash (less taxes) in ten yrs.Many more variables to come into play, but what do ya'll think about the seller finance route to ease my investment diversification fears and spread that tax impact?

There are a lot of variables to consider, but this has been the general consensus from the investors I have been having conversations with.