What are some little "inexpensive" add-on / upgrades can I do to the home help increase the rent while at the same time giving them the security that I am trying to make this place better for them?

You need to concentrate on improving your employment situation and increasing your income.

So when rents move up from $500 per apt back in the year 2000 to around $1,900 today for one of my buildings, the value of the building increased from $140k back in 2000 to $1.4 Million today.NYC is a Future Value (FV) play.

@David Cruice Primarily because i like the cash flow on the property where it is so i don't want to increase the monthly payment or see a rate increase. 

You'd be better off partnering with one or two other people in a deal this size to increase returns for everyone.

When the cost of money rise (higher interest rates) cap rates increase. its simple investment fundamentals.  

If you do go, it's because you have a sick relative somewhere who needs to see you before they go on to glory -- the best kind of story for that is an expensive one, like a blind half-brother with a rare blood disease who is only free of constant pain in this one remote high-altitude institute in the Cascades...something so outlandish no one would make it up that at the same time implicitly explains why you need the rent checks to be on time.

As for learning how to increase your current cash situation you should listen to the BP Money podcast. 

I have recently requested to have my PMI dropped on my primary residence because I believe the value of the property has increased enough to merit the PMI cancellation.

I have rent increases annually at 7% a year to get to market rate by year 4.