Here is a wood fired heat exchanger that I made for my outdoor hot tub. 

Plan on HVAC too as most cities will require a permanent heat and/or cooling source depending on your locale for the electric permit.

We did the required heat treatment and waiting period but were out 4+ weeks of revenue in our busiest time. 

Hello BiggerPockets Community,I am working on a renovation project to replace a central heating plant with decentralized heating, cooling and domestic hot water and would love to hear about other people’s experience with this type of project.The building has 15 one-bedroom apartments and is located in Connecticut (climate zone 5).

Some general info on insuring the property:Here are some things to look for from an Insurance prospective:1.Any in-ground tanks (active or inactive)2.Any Knob & Tube or Aluminum Wiring3.If built before 1978, does the building have Lead Safe certifications4.Any wood stoves or secondary heating units.

I upgraded the 3rd floor heating system from an old steam radiator to a forced hot air system.

I'll keep it short:We put a used stove in a tenant's unit.Tenant complains the stove will not heat to more than 350 degrees.We decide to send a repairman over because these tenants have been high maintenance and we want to minimize contact with them beyond what is necessary for our immediate response. 

So even elements that don’t appear damaged can be contaminated.

A little reading on the elements of adverse possession can guide your decisions, -until you decide on the method you intend to use to acquire the property.   

Asbestos and/or lead paint & Underground tanks (even if they are inactive) are also problemsKnowing when the Roof, Electrical, Plumbing and Heating were last updated (even if only partially) and what was done can help when your agent is shopping the property to different companies.