It will be critical to determine if they intend to include an "amortization" clause, which will require existing STRs to come into compliance (or seek to exist) within a certain time frame.

I was thinking on adding a 4th room without adding sqft just to the existing sqft of 1500.

In this article, you will be able to get a good idea about whether it's better to build new or to renovate the existing property.

If the ask price is at full retail value of the existing condition, I would argue that the seller would be getting too much with that plus equity stake.

I am looking to replace the existing HVAC system in the attic of an 800 sq. ft. single family home that’ll require replacement of existing furnace and new ductwork.

My guess;   Distributing 401k assets to the existing operating LLC smells like the better idea. 

Ask questions of each and get recommendations from existing clients. 

Check with local government on any pending or ongoing discussions on regulations or existing ones.3.

I would set it aside just for the purpose of BRRRR and nothing else.2) Between the equity in my house, and the cash I already have saved, I will have enough to begin my real-estate investing BRRRR journey if I can find the right deal.3) The interest rate on my existing mortgage is 4.5%I'm very anxious to hear your thoughts and sincerely appreciate any help or advice you could give. 

For me, it is quite honestly worth the money to save my mental energy and work on acquiring another property or find ways to add value to my existing properties.