Pine is toxic to snakes and I assume most trees in the pine family are as well (fir, cedars, cypress, etc.). I'm currently looking at building a 5 tier stack with dimensions of 6.6' high, 40" wide, and 17" deep. This weekend I went and got wood prices and what we're looking at right now is aspen. It's harmless to snakes as most people know and use it for their bedding it was around 40 bucks for each side of the viv so I mean it would be cheaper than that. Also most lumber stores I've been checking out also have popular, oak, cedar, fir and I want to say hickory ( hickory is a slightly acidic tree so not sure if this is a health concern as well). Oak is a good solid building material but you'll pay a heavy price for it. If you see a cheap lumber its most likely pine then from there I've seen in price its aspen>cedar>fir>popular>hickory>oak. Staining I'm not certain on so I don't have an answer on that. I imagine as long as it wasn't stained on the inside and was allowed to air out before use it would be perfectly fine.