I told the parents to monitor their kids, but they barely made any effort to correct them.

I'm sorry I can't put a link here, but BP for some reason monitors external links and does not allow them.  

If the seller won't let you then make sure in your agreement that you can monitor the loan and it allows you to pay on the sellers behalf if they don't pay the lender.  

This is so common now that it should not surprise anybody.That all being said, vacant houses need either security systems or daily monitoring.

It's a home run but it needs about $200k of capital to fix some of the recurring infrastructure problems.  

This is a general response, naming attributes, based on your post and what I would want personally:-Monitored, police response -motion sensors in appropriate areas-cameras both indoor (public areas)  & outdoors - motion activated, records to cloud, holds for minimum 48 hours, w/ audio capability-remote light switch control-remote alarm mode settings : on, off, at home-remote lock / unlock entrance-remote doorbell camera (service, delivery interaction)-temperature & flood sensors around appropiate areas-alert capability (various) set for your concerns-ample exterior motion dection led lighting, some solar powered lights that illuminate all night-phone app that you are comfortable usingThere are more attributes I would want but I'll stop here. 

You would, however, have to always monitor payments closely and file for eviction quickly.

I actually think that is one of the best ways to monitor the lower end market.

Also, you can get a wireless motion sensor security cam/monitor with phone app. and that you can actually talk into it.  

Think about how you would monitor payment and period covered.