Tenant + tax appeal + LLC

Hi, 

i am very new here, but i would like get some guidence in regard to recent tenant whom signed lease of 13 months then changed her mind. What would happen in this case? Its the first time i be in such situatio. And deposit already given to the agency. 

I am aware everyone is noticing increase on property tax, has anyone done appeal for reductions because that will reduce insurance as well. 

lastly, in regard to putting LLC on property worth it? If so what would be Pro and Con

greatly apprecaite your responses