This is what you should be considering, yes they are expensive, but you could get your dad to build one for half the price and perhaps a little less elaborate., and smaller, you don't even need to have the upstairs, just on the ground, but then if you have snow then these probably are ideal, unless you intend to bring them inside then, these are rabbit hutches, so something on a slightly smaller scale would suffice.

As you can see this one is built out of expensive materials, you could build out of much cheaper materials, I think the plan is excellent.