As long as the place is well kept, and she is is politely paying the Rent + Late Fees in a timely manner (by 7th or 10th at the latest)...... let it be, however be happier if you were to increase the rent amount.

All my business is word of mouth.

One thing I did learn from that experience though was open your mouth.

I can't get it from the horse's mouth here as to the regulations, but supposedly if you have a septic tank fail and the county learns about it, you're on the hook to remediate the damage and then connect to the sewer.

ALSO these complaints sound like someone who feels like they are paying too much or someone who would be happier owning their own place. 

If you can hold this first property thru your career, I promise you will be happier than if you sell it to move up to bigger and better... there is something special about the first one so keep it if you can.  

The plan was to buy my first investment property, do the necessary renovations all while working to sustain my family without living hand to mouth.

One famous case reported some years back, discussed on another site, the Porter Case, fits this pattern: Porter caseTrue, banks keep their mouths shut when they get paid.

Wow"all the time.That is awesome word of mouth marketing.

(Not being rude, that’s from their mouths.