After she takes inventory and assess  the damages, we will decide what to do going fwd. 

Even looking here in the Biggerpockets marketplace, pick out some properties and practice analyzing them, so down the road YOU KNOW what a deal looks like.

That said, I'd love to hear how the BP community assesses medium to long-term (5-10yr) prospects of apartment rental markets? 

Welcome Valente,It's a broad question with a lot of different answers, but I'll do my best to help you find some.Before even thinking about which real estate strategy to employ, I'd start with an honest personal financial assessment.

One of the units owners has not paid assessments in over 10 years.

In genera what would have done is wait the grace period out and then send a text saying per the terms of your lease you have been assessed a late fee however since you have never been late before if you can get the rent to me today I will waive the late fee.

For me FB market place has been the best place to advertise rentals.I like using ZIllow applications so I might pay for a week and tell everyone to go there and apply.

In Indy, for non owner occupied properties, they are about 2% of the assessed value.If you find insurance for $400/year, please let me know where.The one thing you can count on is that the pro forma numbers a turn key seller gives you are not going to materialize.

After assessing it was clear to us he'd make around $8-12 and that's over 8 months!  

Also, the link for the Bergen county tax assessments isn't working for some reason.