You could sell this property, but you'll definitely have to disclose this and the process will be more complicated.

...wait until you hire an amateur.This is what the amateur gave me.This is what the expensive pro gave me.

My guess would be the tenant would still be liable since the mechanic's lien involves work done by the tenant when hiring the contractor. 

Start this process so that they know that is an option and available to them.

Ask them the same questions and see how their confidence, approach, process, and solutions vary.

We then talk about logistics for our upcoming relationship; how to pay rent, how to submit maintenance requests, emergency maintenance request process, HOA restrictions and violations, confirm they have switched utility accounts over, and other pertinent facts about how we manage homes.Finally we collect move-in funds and exchange keys.Welcome to the game!

Focusing on profit rather than top line is always my guidance as it encourages you to automate and streamline processes, which often leads to innovations on the guest experience front. 

I did not have to hire a property manager and pay them lots of money to deal with it.

Last time I did that, my costs came in right at $1000.The OP is vague because it does not address size or location of heater, type of fuel, self-install or hired, permits required or not, and whether or not they care about a specific brand.  

Our last email from Alan confirmed our suspicions that we were getting jerked around by him admitting that it was his fault that the refund process was dragging on because he ‘knew what was in our best interest to do’ and that was for us to relaunch the program instead of giving us a refund.