We did live in a SFH converted to a duplex as renters before we bought, and aside from the upstairs tenants having a dog against the lease we got along well with everyone else who lived there.  

Behavioral economists call this kind of behavior anchoring.

A bird-dog I use often reached out to me about a potential condo deal.  

@Victor Mejia Well in virtually all states being a Bird Dog, as i would define it, it illegal.

What you might really need is a local investor friendly agent, partner, or bird dog that can help you out.

If they don't, they have cats or dogs or want a move in date that does not work.

MLS, bird dogs, (people who hunt deals all day long and you buy leads from them) , buying public records from local court houses in your area of interest, records on divorces, foreclosures, etc.

Is that common behavior?

Plus numerous outdoor improvements to improve curb appeal and landscaping, add a dog run, and improve lighting/security. * Over time, we'd spend $7500/unit to upgrade interiors as units turned over.

I encourage you to investigate the methods but there's a human behavior called "analysis paralysis".