As always, your organization is on the cutting edge and not just blathering out corporate-speak.

I had refinanced all the refi fees into the loan so many times that it cut into my overall gains when I sold it.Bottom line, don't take a good look at the big picture and not just the increase in cash flow.

That's a lot of cash to tie up for the return you'd get. 

This allowed us to cut the cost of our rent substantially.At the apex of the rental year in Washington, D.C., we can net $2,800 a month just by renting out our basement.

The pre-construction will tie up your cash with out cashflow til it is complete and there is risk associated with pre-construction.  

Worse case scenario is that ALL of my cash will be tied up if we cannot refi for any reason.

Our existing mortgage on that house (15 yr at at 4.25%) will be paid in 6 years and yesterday I was quoted a rate of 4.75% for a cash-out 30 yr refi.Tax considerations: we've owned the existing property as a sole proprietor and the Tax Cuts and Job Act has me considering LLC or even possibly C-Corp for tax benefits.

With federal cutting the rates to zero, what to expect on high balance mortgages (loan amount above 500k since its pretty common in bay area). what interest rate to expect to refinance and new home mortgages ?

While I am not surprised rates were cut to zero - bank reserves were also cut to zero as well.

That will likely do more for the market than another rate cut.