If you want to 1031 exchange to a property outside of CA, then you'll want to be careful about how the California Franchise Tax Board makes 1031s more difficult (no surprises there) when leaving their jurisdiction. 

I would like your opinion on whether it would be better than finance the whole purchase with a HELOC from my primary residence or only get the down payment from there and get a traditional mortgage for the rest. 

With a minimum 30-day rental period, tight registration criteria limited to permanent residents, and associated compliance costs such as fees and taxes, entering San Francisco's STR market without first examining these restrictions may result in problems and severe fines.

Amit,I've heard of it, but I'd be careful. 

Unfortunately, upon doing some initial research (including on biggerpockets and reading Brandon's book on real estate investing), its not always feasible to invest where we reside - do you alternatives in mind?

I have reason to suspect the trustee also has a title with her own LLC, a Land trust, or some other form of separate ownership documents for her self on this property, and hasn't told me or my sister, who knows nothing about real estate, and doesn't care.

I primary residence with a duplex in the back.

I'm also building an ADU here at my primary residence that we'll operate as a STR.Of my Detroit doors, 3 are Section 8 and one is operated as a STR.

I have house hacked 2 single family homes in Colorado Springs, moved out with both rentals cash-flowing very modest amounts annually, and am actively looking for the next property around Allentown, PA.My 2 options: Add to my portfolio and House Hack for the 3rd timeI know that house hacking will be the easiest barrier to entry around a big down payment, has the chance for a lower APR with a primary residence loan, and I am comfortable using this strategy as I have done it twice in the last 3 years.

I don't know who that is, so I might be wrong but be careful with those kinds of programs.