Unless you have the wood working tools and patience to build out of either wood or pvc, just buy one. I have a PVC 4x2x2 from custom reptile habitats and it's WELL worth the price. Solid as all get out, assembled in minutes with nothing but a screw driver (in my case a drill with phillips bit on a very soft clutch setting), and I carried it into the next room by myself after assembly. I was happy enough with it that I just ordered a 3ft enclosure from them as well.
If you must build your own for whatever reason, go with wood. Easily sourced, seal it with pond shield (amazon) or drylok. Even the clear acrylic doors, slide rails, locks, and little handles that stick on are on Amazon. I found a ratty looking 6x2x2 unfinished wood enclosure at my local pet shop and bought it for 350, and have been upgrading/finishing it at my leisure.
Pond shield: Pond Armor SKU-BLACK-GA Non-Toxic... https://www.amazon.com/dp/B00HYVC8F8?ref=ppx_pop_mob_ap_share
Lexan because scratch resistant: Polycarbonate Lexan Clear Plastic... https://www.amazon.com/dp/B00AWTE72G?ref=ppx_pop_mob_ap_share
Slider tracks: Randall Manufacturing 1/4"... https://www.amazon.com/dp/B08MBFDVHK?ref=ppx_pop_mob_ap_share
Door locks: Qjaiune 2 Pack Sliding Glass Door... https://www.amazon.com/dp/B09CWFYNLV?ref=ppx_pop_mob_ap_share
Pull handles: Self-Adhesive Pull Handles 4... https://www.amazon.com/dp/B09GMK92MC?ref=ppx_pop_mob_ap_share
Stainless mesh screen: 2PACK Stainless Mesh Screen... https://www.amazon.com/dp/B086YSDNSR?ref=ppx_pop_mob_ap_share
External paint: POURING MASTERS Jet Black Acrylic... https://www.amazon.com/dp/B07ZFZV9MS?ref=ppx_pop_mob_ap_share
My favorite environmental controller (I have 4 of them, one for each snake!):
REPTIZOO Digital Thermometer... https://www.amazon.com/dp/B07RDDQJX1?ref=ppx_pop_mob_ap_share
Fogger that's been good to me so far: Reptile Fogger Terrariums... https://www.amazon.com/dp/B07VVNP7F3?ref=ppx_pop_mob_ap_share