Getting a bit overwhelmed with all the required County Level and City Level business licenses, STR permits and Tax accounts (Business Tax, Franchise & Excise Tax, Sales & Use Tax) to register with the state.

You can create an account to advertise yourself as a host or a guest (or both) and get matched with others.

Yes, but your "highest and best use" is being an accountant to your clients, not handling the minutia of your RE portfolio!

If it's a fixer upper you would account for the rehab and purchase price then compare against the ARV.

How would this be accounted for for general accounting and taxes?  

I once made the mistake of chasing multiple listings at once, which turned into a disaster.When I shifted my focus to serving one client at a time with honesty, integrity, and accountability, referrals started coming in without any marketing.

Accountant – Preferably a CPA. 

I have a large lump sum saved in an investment account for down-payment and any additional costs.

Yes to avoid taxes and penalties (under 59.5) the money would need to stay in the retirement account.

However, I got caught up during creating my listing because it looked like I needed to have another account (Stripe?