As a corporate senior leader with organizational development and design experience, I made the company millions while only earning a measly $100K+.

Be mindful of the fact that unless you are dealing with a seniors or higher quality community your tenant pool will be primarily C-/D class.

My father in-law rent out his house to him with a much lower rent, he couldn't keep up with the payment and did 't keep up the place and the police were called many times to visit the property.

All they need to say to the police is, "I am a tenant" and the issue becomes a civil manner.

Hello,I was wondering if I should go to real estate school online since I'm currently in my senior year of high school going Full-Time or what till the Summer and go to real estate school in person?

Police would not do anything unless they saw something happen, even after multiple complaints, and wouldn't even check into that 16+ people were living in a 3 bdrm home, stating they could just be guests. 

There are no HUD police that check up on Owner Occupant purchases. 

I need to obtain landlord insurance in upstate NY multi-family (2 units) Thanks a million  If you know it is a pitbull and it is illegal to have one in your area then you can call animal control or the police.

For example, if I called the police department in my area and told me that someone broke into my property, they would probably treat them as a trespasser and remove the person from the property.

This type of disruption with neighbors, guest they have, is thier doing and you need to enforce compliance.I would non-renew and make sure you let section 8 know your not renewing their lease when you do that.Crime Free / Drug Free Addendum is a great tool to help control what goes on for a owners property.You might also get copies of police reports for incidents on your property to back up the disruptions.