A while ago I made this terrarium which is sturdy, lightweight, nice looking (personal opinion) and still cheap to build (I spent cca. 100€). It wasn't hard to build either, for someone with some experience.
Dimensions of this terrarium are 100x40x40cm. Rear and lower plates are made of 12mm waterproof plywood. While the top and sides are made of 6mm waterproof plywood. The cover is made of 4mm plexiglass. The dimensions of the terrarium and used materials can and should be changed to suit needs of future inhabitants.
The aims were: the final product should be reasonable lightweight, materials should be of good quality and animals (and people) friendly, while still be reasonable cheap.