Are there any weird laws in Florida where if sellers stays on as a tenant, can I lose the property?

You would probably need to hire a lawyer and you are likely to lose much more than the cost of a utility bill or two.You may also want to have a conversation with her to explain your situation. 

I want to take a Heloc but always was scared of it...I want to open it just in case, sort of like if I lose my job, etc...1) Do I understand correctly, if I open a HELOC but do not borrow the money, then this I do not owe any payments to the mortgage company?

When issues came up and I was losing sleep at night it was really nice to be able to drive to the property to help mitigate problems. 

I stay away from offerings with a higher minimum because it's more money than I want to lose if something goes wrong.In exchange for advertising a 506(c) offering, I believe you have to verify accreditation.

They state that the treatment last used (one building 1992 and other 1996) is losing effectiveness.

why not hold onto it through the recession and break even or lose a little bit each month instead of losing thousands?

So you could bill tenants at $6.24 per unit.The other crummy way the County bills for water:  there is no online portal for bill retrieval and if you lose a bill you must contact the city to request a water billing history. 

We ask for 30 days and they lose their security.

And most likely they would lose their license.