Also, for anyone based in Philly, I've heard from one contractor that quotes of 20-30k were common a few years ago, but due to recent rule changes, contractors need to maintain excavation licenses/ insurances to do any dig out work and that cost is getting passed to customers.

If you don't plan to work anymore, you may want to consider the rule of 55.The distributions from the retirement account will be taxable in one way or another(now or later).You want to plan it in a way so the overall tax burden is less. 

I would also order a foundation inspection or sinkhole report prior to purchasing, if you don’t that fight with the insurance company is a "No Win" situation!

I am currently living in Missouri; I have one house rented out and am planning on getting more.

From there you can submit plans/permits, and from there you can begin your rehab.

In theory yes, but it does not make sense from a tax planning point.

I currently house hack a duplex that I plan to cash out refi soon to repeat.

They are rentals that are both cash flowing and under lease until next May, at which point I plan to rehab and resale.

Cash Plan to refinance when rates are more favorable How did you add value to the deal?

Planning.