Don't make any modifications to the land until you are ready to build. I don't know what the full definition of "unimproved lot" would be, but clearing land for construction site, adding roads, etc definitely sound to me as improvements. Those improvements will have a not friendly affect on your taxes. If your plot is big enough, add the minimum number of head of some sort of animal to possibly qualify for ag exemptions.

Lots of games to be played that you might be unaware of to keep from slowing the growth of that nest egg.