For example, could you scale and have the security of modest cashflow (somewhere between 2-5% after all expenses, including CapEX are accounted for), if you put 30% down? 

My payment (including escrow for insurance, taxes, etc) of $2500 would go to roughly $4500.

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 law imposes duties on the landlord including: Abiding by any applicable housing codes (including state, city and/or county codes), and maintaining the property in a safe and reliable manner.A tenant can sue a landlord for a slip and fall as long the tenant can prove the landlord was negligent and the negligence was the cause of the tenant’s personal injury (broken or fractured bone, scarring, or another serious bodily injury).

There's a couple of things that make this more attractive than the other option sugggested of forming a new LLC to own the property.First is the expense and reporting involved in another LLC entity.Second though and more important in my book is that by having your LLC own a TIC interest and having your partners LLC own a TIC interest you keep the utmost flexibility available to you as you move forward with that property to eventual sale and possible 1031 exchange.  

Whether you’re a seasoned investor or just starting out, location is one of the most important factors to consider when investing in real estate.

Then I thought I could buy the house from my dad for $300,000, which would include the money needed for the rehab instead of doing 2 separate loans.

That's probably the most important question you need to ask yourself - are you willing and prepared for that outcome? 

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