Ideas for a couple cages?

I'm looking to build my first cage setup now that I've got 2 snakes, a ball python and a young corn. I have a few questions

What is a good size cage, where I can comfortably house a full sized red tail boa in the future?
What is the best material material in terms of durability vs. cost?

Any ideas would be great, I'm looking to make 2 seperate cages that can be stacked on top of each other or by themselves. If I make them too big for my corn snake, I can put some false walls in somehow.

Thanks!

in the future for a redtall 6x2 im talkin when hes 9 to 11 feet fulll grown but untill then you can keep him a 4x2 untill hes about 7- 7.5' . materials. im a fan of 1/2 Birch and useing popular wood to make door and door frams out of. cost for a 6x2 they way i would make it would be ruffly 150-200 bucks. when glued and clamped tightly with a screw here and there or nailed with finishing nails (which i just use my nail gun)


how big is your boa????