If you do not apply by today and you are going to use your home/cabin as an overnight rental, you will be required to bring it up to current building codes.

ive always just used an excel spreadsheet with coding to categorize the expenses 

Remember there is a difference between work done to code (good enough) and work done per best practices.

Then if 50% of bookings actually use the "included add-on" with a standard $100 coupon, that's $2000 in services I have to fulfill (for now I'm assuming they all use the full $100 but I'd set it up where it's a discount code and I charge for any extra amount).

Key code?

But any plumbing or electrical I don’t know what’s code 

Is it a good idea to incorporate logos, portraits, and QR codes for direct access to my site? 

(California Civil Code Section 1947.3).

Use a smart lock so you can give temporary codes to all of these people. 

I have decided to focus on Memphis, TN (specifically 38111 zip code where the University is located).