What breed rabbits do/will you have? All-wire cages that are stackable or hangable are best, though I have always purchased mine and don't know how easy they are to make yourself. Wood is not generally a good idea, as it is hard to disinfect and would need a covering of bedding, which also isn't very sanitary. Wire cages allow all droppings/urine to fall through, enable good airflow, are easily cleaned, and last for a long time (unlike wood, which gets dirty/chewed). Most rabbits will have no problems with sore hocks on wire cages; only extremely heavy breeds (like Flemish Giants) or those with genetically-poor foot padding (like some Rex/Mini Rex) should be kept on solid floors.
As for size of cage, it varies with the rabbit. I keep Mini Rex (3-4 pounds) in 18" by 24" cages and Sables (7-10 pounds) in 24" by 24" or 30" by 24" cages. My pregnant/nursing Sables live in 36" by 24" cages and my pregnant/nursing Mini Rex live in 30" by 24" cages. They need the extra room because their nest box and kits take up a lot of space. All my rabbits except maybe one have never had problems with sore hocks. None have had bone deformities. And, none of them have seemed unhappy with their size of cage, or become too fat due to living in what some may consider too little space. Most weight problems can be corrected with diet/pellet portion size, rather than space provided.
