Recommend cutting your teeth on a single family, then go from there.

Lots of low income people with literally no front teeth. 

Even if you just had one tiny old lady living upstairs, it can sound like an elephant when you're downstairs, and some people are more sensitive to the sounds of someone walking around above them - I'm one of them, which is why I only rent the top floor unit when I rent.Is there any way you could get them to swap apartments? 

Here in Boston and generally around hospitals medical residents tend to be great low impact tenants: All their time at work or sleeping, generally not too price sensitive (whats another few hundred when you have 300K+ in loans?)

I use rentprep.com so I opt for the feature that allows the landlord to request the applicant to fill out sensitive details online, and they pay for it directly online.

Is this shady or just someone whose hyper sensitive to his privacy?

All it will take is a couple of kicks in the teeth for you to say screw this, were going back.

When it comes to audit-sensitive areas like STR and REPS, I think the best bang for your buck is to pay someone to do it for you who has been doing it for years. 

Real estate investing is hard so be ready to get kicked in the teeth.

Your question will be answered and debated many many ways, as there are multiple approaches to your path there.I would suggest finding a seasoned wholesaler in your area and trying to help them with their deals to learn quickly and sink your teeth in on some real-life action.Me personally, I would start on by finding SERIOUS PROVEN BUYERS, which you can find at your local REAs.