Like privacy and good maintenance and mostly leaving them alone.  

Most people prefer having more space and privacy with SFR, so they are usually choosing multi's due to the lower cost or ease of qualifying.  

Any privacy or safety issues?

Make sure you're ready for problems that might occur like these.....for example... guy roommate walks into bathroom while female roommate is in the shower, guy roommate walks into female's bedroom while she's sleeping, guy roommate goes through female roommates things while she's at work/class, etc.... they're going to be calling you, because you put him with them even though they told you they weren't comfortable with him and now all 3 of them want to move out because he's invading their privacy and there's no way they can live with him. 

If the neighbor is making an issue of it, the best thing might be to make sure everything is out of his sight with a privacy fence.

You should respect your tenants basic privacy rights and unannounced random visits violate what is considered kosher in most locales.

(sure; we can expand the privacy fence into the alley. 

In the other the neighbor had a chain-link but was a total slob and I didn't want anyone to see his mess, so up went a privacy fence. 

A good form of privacy, but not sure about legality.

It is also possible the municipalities are not providing access, either for reasons of privacy, reasons of profit, or reasons of being late to the party and behind with the times...hmm...Search: land records, GIS, mapping, property records, real estate, real property - who knows how the municipality has organized and named their records.I will leave you to it and good luck!