Do you research here, attend some of the local meetups, and be patient most of all.  

Definitely need a patient seller. 

The smaller the better.Be patient - since each bank will call the shots on their own money that means each bank will decide on how to lend the money differently.  

There is only one situation that I can think of where I would even consider a tankless and that is where the current water heater location is no longer suitable (i.e. you need the space, or there is some safety concern).  

If it is a rental add some treads for safety.

Keep seeking and you will definitely find the right agent/agents who will NOT blow you off and will be patient with you (I have).

@Marian Smith  #1 most don't redeem#2 they do not have to reimburse you for improvements that were not safety/preservation oriented.  

Be patient, get some good feedback here but don't forget to assess your time, skills, money and temperament to factor into your decisions.  

You could also ask the bookkeeper which CPA does he/she collaborate with and then verify the competence level with with the CPA.If you are concerned about the safety of your financial documents, most cloud based accountants use software (Quickbooks, file sharing services, etc) with bank-level encryption. 

If you can afford to be patient, time is on your side.