Is it legal to own a tank?

Answer 1

Providing that it has been "de-militarized," it has to be assumed that it is. The problem might be in getting it there and moving it afterwards. The weight of it might prove to be a problem in driving it on the roads and over the sidewalk to reach the street and the treads would have to have rubber blocks affixed to them to prevent it from tearing up the asphalt.

Answer 2

A tank of what? Compressed gas? A tank of propane? A tank of water? A military tank?

There are laws about what can be stored on private property and how it must be stored. An operational tank would not be allowed.