Are you concerned about tenants leaving prematurely though?  

From your description, it is possible the burner needs cleaned and serviced and stopping operations just allowed buildup to harden and/or break loose and become an obstruction - or a spider decided to make its home in burner {we had a furnace not relight as a result of this once} ... though at 2(ish) years of age, it shouldn't be that dirty.While it is possible a sensor has failed prematurely, I'd start with a service.

Best of luck and (premature) welcome to Houston! 

Any charges you could even consider would be heavily pro-rated based on the current age of the unit vs the average life expectancy which is typically cited to be around 15 years.And then you need to prove that the lack of filter change caused the unit to die prematurely before average life expectancy....good luck with that.....The "change your filter every 6 months or it will kill your HVAC" is WAY overblown....a marketing ploy by HVAC repair and filter salesmen.

What happens if one of the members becomes disabled or passes away prematurely?

Tracy,You could take a distribution from your IRA and are free to do anything you want with those funds, including paying off your rental property, but that is probably not something that you'd want to do nor would it be a wise move (because of the huge tax hit and penalties in case of premature distribution). 

It is premature to argue about the 'service animal' at this point. 

A security deposit may be used only for the following purposes: (1) To reimburse the landlord for actual damages to the rental unit or any ancillary facility that are not the result of ordinary wear and tear. (2) To pay the landlord for: (A) all rent in arrearage under the rental agreement; and (B) rent due for premature termination of the rental agreement by the tenant. (3) To pay for the last payment period of a residential rental agreement if a written agreement between the landlord and the tenant stipulates that the security deposit will serve as the last payment of rent due. (4) To reimburse the landlord for utility or sewer charges paid by the landlord that are: (A) the obligation of the tenant under the rental agreement; and (B) unpaid by the tenant

Thank you so much to all who took the time to respond.I think I posted prematurely.

Felt as though I wasn't ready in other aspects to move forward so why be premature.