Checking: collect all income here, then use it to pay bills.

It even gave suggestions on what I could improve based on what my competition is offering.Link to the operator in action is here https://drive.google.com/file/d/1C1uTqgWGfs3AMsUdDWd0FOTbVFM...Quick tip: don’t pay the $200 for this just yet.

If they don't pay willingly, what are my options? 

The interest rate isn't that huge of a difference between the 15 and 30 so worst case scenario if you have the 30 year option is you start paying it down on a 15 year timeline - sure you'll pay a little more in interest over the 15 years, but it will have been worth it if you bought another house.

If you achieved this by paying all cash, then you are losing money. 

Somebody somewhere had to pay for that real estate at some point and has continued to pay for it since.

This is a the perfect vehicle to use for short term like buying a  property with cash, then refinancing the property to pay the line of credit back in full, and use it again.   

@Cole Starin sometimes it makes sense to sell the WORST property in your portfolio.Another option is why do a LOC on the duplex, when you could just do a $100k cashout refi to pay off all your debt AND keep the property?

Also, don't forget that, if you pay taxes, it means you're making a profit.2.

Regarding your other questions:  - If the going value is $260/SF, why would you pay more than that?