Building a solid team is a smart priority, as real estate investing is much more efficient when you have a trusted group of professionals→ agents, contractors, lenders, who understand your goals and the local market.Your plan to own four long-term rentals in the next four years is both realistic and attainable, especially with the type of property you're targeting.

They've mentioned they have asthma and allergies and that's why they're upset about have to live in a place that's being repaired, so I've offered to both hold off on the repairs and reduce rent to make up for the condition of the property, I've offered to have a contractor just rough in the drywall so that the studs aren't visible and to encapsulate everything, even though everything in the cavity was removed during the remediation, but they now aren't responding to my texts whatsoever.

Agreed - its generally a bit more challenging if its true "student housing" as rent-by-the-room is generally prohibited for DSCR. 

It's a way to get consistent and often top of market rent for your properties.

Should I stay away from these old SF properties?

Good income producing property.

Be sure you are using a non Wholesale lender for the true DSCR experience.Cheers!

Any recommendation on hot spot location to search for properties for fix and flips??

Is there anything I need to do, or be aware of when buying an occupied property with section 8 tenants?

I recently bought a $1,250,000 property and only had to put down 5%.