any recommendations for stacking 4x2x2s?

i currently have a baby boy in a 40gal but he’s about to outgrow it so i am moving him up to a 4x2x2 soon. i know a guy who buys/sells/trades lots of reptiles and tanks, and i can get a 4x2x2 off of him for like $30, but i’m looking for solutions to stack them as i’m looking into getting another baby soon (they’re addictive!). any ideas or shelving units you guys know of that would work well for stacking 2-3 4x2x2 tanks? i’m gonna go for front opening as i don’t know how this would work otherwise and it would also just be easier. i’m ballin’ on a budget so any affordable ideas, especially incorporating whatever tanks i can get my hands on from the guy i know would be extra appreciated!