Like Cosmoboa I prefer the laminated plywoods. Birch (or maple) gives a very smooth surface that accepts paint or stain nicely. Oak has a very rich grain texture that looks fantastic with a stained/clear coated finish.
Regarding doors, that's totally up to you. I much prefer double sliding doors I build myself. They work much better than the doors on many commericialy produced cages. If you prefer flip down or hinged to the side doors, by all means use them. I do have a preferred way to build hinged doors that I'll happily share if that's what you want.
For a BP you could probably get away with a water based stain & polyurethane. However, I would provide something a bit more durable for the floor. Perhaps cover the floor with expanded PVC. This will make it easy to clean and also be resistant to water spills and feces/urates deposited on the floor. With it's excellent thermal properties it is also an ideal material to use in conjunction with sub-floor heating (aka "belly heat"
.
I know you've indicated you want to use RHP but having the ability to add sub-floor heating is a good idea since your winter room temps are low.
There are two ways to use a PVC floor. One is to cut a rectangle out of your plywood floor that is a couple of inches longer and wider than the largest UTH you'll use. Then the plywood floor is covered with the PVC and there is a 3/4" deep air space below the floor to add an UTH if you need it.
If you're confident in your construction skills you can forgo the plywood floor and simply attach the PVC floor directly underneath the cage. This saves a lot of weight but you lose the structural integrity of the plywood floor.
I've done this with dozens of cages with great success.
The PVC floor will make the floor itself easier to clean. The main problem is the junction between the floor and the walls - the area that snake always seem to use for deficating. A water based poly will not withstand scrubbing very well. This is not a huge deal as it dries so quickly that you'd be able to touch up those areas a couple of times per year. One option would be to line the first couple of inches of the walls with something more durable. Either PVCX, an oil-based poly, or perhaps some contact paper that matches to color of your stain.
I think you can keep the costs of any of the above options below $150. You probably could even if you paid a high-end cabinet shop to cut the material for you.
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Build a 3' by 2' by 2' (LWH) BP cage.
have it heated with a RHP.
my room temp goes from the low 60's in the winter to the high 70's in the summer.
can someone answer these questions?
what type of wood do you recomend?
what type of door do you recomend?
What type of sealant/stain do you recomend?
how will i make it easy to clean?
I want it to cost less than $150 (just the cage). and i want it to be insulative for the cold winter.