depending on how energenic you are..you can make a pretty nice one..even insulate the walls if you want..
using a pallet as a base..and a big melon crate we were able to make a big dog house for my dads
great dane..there are alot of scrap plywood you can pick up around building sites..*be sure to ask*
and roofing material as well that they re just going to dump..
now, if you have more money than time...id go with the one from one of the box stores...
i just looked and there s all kinds you can get..