we ended needing 3 to cut the boiler, 11 radiators, and all the associated pipes.   

I'm looking at a 4 unit that has these big floor mounted radiators, are these expensive utility wise?

http://www.epa.gov/radiation/radionuclides/radon.html

There's a crack in the microwave door, and the tenant is worried about radiation leaking out.

Having asbestos in your house is not like radiation where you get contaminated by near proximity.  

We had been going to hotel Lorraine to pay rent and supposedly pay rental ins that later found out after all of our belongings were destroyed due to them not paying gas or water and it blowing all of the radiators in the entire place.

And would not work on radiator piping or radiant floor heat piping. 

Also check if there is an issue with certain breeds with your insurance company.Having just finished cleaning dog hair from all the baseboard radiator fins in every room in our soon to be rental I am very much in favor or a non-refundable cleaning fee for pets.We are debating pets at the moment for this house as it is the right kind of location for it and has a big backyard but I am not offering it in the ad.

Even in our northerly (read long, cold winters) climate, a modest (8-10K installed) solar thermal system met 60% of the DHW needs of a 6-unit building and meant the boiler did not need to fire at all during the summer to heat hot water.Such a system can also be used to pre-heat the return lines of a hydronic baseboard/radiator heating system lessing the load on the boiler.  

It is the middle of winter, my first thought was you have some sort of radiator steam heating system which can generate all sorts of knocks, bangs and loud noises through the pipes.