This problem came to my attention when me, tomreyn and titi-son were playing the latest prax game (0.5.9). titi-son started to build a new building that was recently added, and it was only after it was built could he see that it could store gold.
Currently, when you hover over one of the "build a particular building" selections, all you are told is its cost. What I recommend is that when you hover over one of these selections is that it also shows you what you would see if you were to select an already built corresponding building (so hp, storage etc.). Except, you don't want to show information such as "Kills" (arrow towers show this when selected).