You will almost always pay more than you initially planned.

I plan to do cost seg study and get bonus depreciation (and will actively participate as per IRS rules) but need to confirm if this would still work if buy STR under LLC and I can still be eligible for that STR loophole?

If you plan on really scaling up, you'll probably want to go with an llc.

Plan to sell all POHs, seller financing, or cash sales.

Do an ARM, buy down the rate or plan for the future refinance. 

My plan is to purchase single family homes/townhomes for long-term rental, and benefit from appreciation over decades.

Hi Lynn,Not entirely sure what your plan is for the property the HELOC is on.

What is plans with driveway?  

The reason we bought the property is that there is an 8-acre clearing at the peak of one hill which is where we planned to build the future homesite as it has an amazing view and a nice, mostly flat area (see second picture for a bit of the view).

We paid off 10 houses, borrowed against them to buy a few nicer houses and plan on doing it again.