I just finished building a cage for my two boys (thinking of adding a 3rd). The cage is 4x3 grids (on the main floor) with a second (1x4+1x2) L-shaped level, and a (1x2) mini-loft. I bought 2 boxes of grids. I used 2 grids for the ramp to the second level, and when the whole thing was done, I had a single grid left over (which became a hidey-house). This thing is HUGE (too big for a table-- we had to put it on the floor), and if you count the shower-curtain we lined it with (no one around here seems to have coroplast) and the zillion cable ties we used to put it together, it still cost me less than $40. We're planning to build one for our ferrets and possibly our chinchillas as well.