Instead of debates and personal opinion, look for proof https://www.ladbs.org/docs/default-source/forms/plan-check-2017/single-family-dwelling-duplex-plan-review-list.pdf under G (Interior Env) which defines the minimum requirement of a habitable room (aka bedroom or bathroom).

investors who have registered with us and provided sufficient proof of accredited status, are presented with the opportunity to invest in a specific series, with the only asset of that series being a single note.  

Definitely do what it takes to add some sound proofing.  

On the other hand, I’m hesitant to simply pay down more of a property, as we don’t need the immediate cash flow.Fortunately, both my wife’s job and mine are recession-proof, which allows us to be a bit more aggressive with our investments.I’d really appreciate advice from investors who have experience with frequent moves or military service.

With no proof required.  

G'Day Alejandro,As a few have already mentioned, take a peak at Toledo also.In my opinion lower potential for long term appreciation but solid/"boring" cashflow.I prefer my portfolio to be "boring" but cashflowing lolLow entry points (Sub $100,000), high rents (Above the 1% rule).Blue collar working class decent folks that will stay and pay.Depending on the area but no derelict homes, yards well kept, cars with wheels and all tenants are employed.Plus, all are sophisticated enough to pay rent online so property management doesn't have to collect rents with bullet proof vests and shot guns lolI'm bias toward Toledo but it's worth considering.Wishing you much success

I also make sure to specify in the lease agreement that I need proof of coverage before move-in and that the policy should name me as an “additional interested party.”

Tenants like to set up insurance, show proof to the Landlord, and then immediately cancel the policy after moving in.

From my understanding, I need a Proof of Funds in order to get under contract. 

It's crucial to maintain thorough documentation of your hours, as the IRS may require proof of your time spent on real estate activities if you claim REPS.