However, while we were cleaning up, we treasure hunted out at least $3000 stuff, including $300 cash on the floor, several un-opened Amazon boxes, new-in-box computer/gaming items, hair tool ($300), YouTuber's gadgets, new with tag heated jacket ($220), an unassembled exercise bench ($500 at least), so many new or near new stuff that you can sell.

I feel like this is suchhh a common question for new house hackers, including myself. 

This reduces the amount of debt you owe and increases your net worth.

I would just budget to fix it and include that in my offer price. 

It's a -14% return if that $800 is before interest ($375k debt * 3% = $13,125 in interest expenses).

I would like to be able to afford my whole mortgage at 100% vacancy in a disaster scenario, which puts me at buying houses less than 200k at the current interest rates including expenses and insurance.

If the numbers makes sense, which likely they will since you inherited the property and there is no mortgage, then renting it out debt free could be a great move right now. 

(Form 1025 for a 4plex which includes sales comps + rent comps)

Almost everyone here on BP will tell you that they wish they had started earlier, myself included.4.

Took HELOC in Oct 2023 for the (2nd rental) to pay off all debts.