Is it ok to make a c&c cage for one rabbit?

Yes, c+c cages can be used for rabbits - but the sizing needs to be different.

the minimum size for guinea pigs is a 2x3. For a rabbit, you should be looking at a 2x6 or a 3x4. Certainly bigger than a 2x3!

Rabbits also need far more height than guinea pigs - they must be able to stand up fully on their hind legs without touching the top - so the cage must be at least 2 grids tall. Rabbits are also excellent jumpers, so you would need to put some sort of top on it (using grids, wire closet shelving or something similar.)

Check out the gallery on the guinea pig cages website to see how other people have made c+c cages for rabbits: http://www.guineapigcages.com/photos/showgallery.p...

Many rabbit people use those cages (although they call them NIC cages). With rabbits, you can build a shelf or level and you can make it taller. The minimum size is 2X3 grids and 2 high. That would be for a small or medium sized rabbit, bigger rabbits do need more space. If you do all levels, they need to be reinforced with a wooded dowel or shelf support.

There are some people who put the guinea pig cage on top of the rabbit cage to save space. The rabbit should be able to go in and out of the cage on its own when allowed (so you don't have to pick it up to take it out or put back in).