No radiators, convert to forced air once they're taken.

Last day I noticed that the radiator is not heating up that well.

One tenant complained that her bathroom flooring was flaking off around the radiator, and since I wouldn't want vinyl sheet flooring in my own bathroom I replaced it with ceramic tile for not quite the cost of one month's rent.

I got a new bathroom framed in, electrical is all set, I now need to rough in the plumbing, move some radiators around...etc..to be able to continue.

My wife and I decided to remove all the radiators and convert to forced hot air furnaces with central air.

Most tenants don't like our restrictions and will gladly use the heating system that we provide.We also keep a few oil-filled space heaters (radiator type) in our tool supply for when we have a furnace breakdown.

The boiler system has baseboard radiator heat & 3 new thermostats that must stay since they were all completely replaced.  

I pulled back the carpets to see if there was a return pipe (as if there was an old radiator line) but there was nothing.

If the latter, I would also plan to separate the heat as common forced air is a conduit for pathogens, allergens, noise, cooking aromas and fire between units - tenant relations are usually better when those things are not shared.If the system is hydronic (baseboard or radiator), then the key bit of information will be whether each unit is plumbed as a separate zone from the others.  

It can get down to 20 below here, granted its inside but cold still radiates in on the floors.