Im also thinking about breeding as well, it seems around this time a few people are. It'll most likely be more than a year from what ive researched. Males can mate at around 18 months i believe with females better off at 24 months, however that is just what ive found. Maybe a more experienced person on that could offer more advise for the right age.
Thats gonna be a lot of 20 gallons for tons of babies so possibly get a rack and some bins, I dont exactly know what a good sized bin would be, but i believe most people use 100 L totes to raise them in, or 106 QT tub. It would most likely be cheaper to go with the bins/totes rather than the tanks, also more light weight.
https://www.beardeddragon.org/forums/viewtopic.php?f=34&t=233480 This is a pretty good post to see how to setup a rearing tub/tote.
If you do really plan to breed i'd setup a few colonies of crickets and dubias beforehand so you have enough food ahead of time, after all if my math is right one single 1-4 month old bearded eats around 1,260 bugs a month. So if one female beardie can lay up to 6 clutches of eggs from one single breeding, 15-30 or so eggs each clutch thats gonna be a lot of bugs needed.
I'd also make sure that you can keep leftover babies in case they dont all get sold.
For incubators I'm currently using this one,
https://www.amazon.com/gp/product/B01MG4166U/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1 Im thinking about getting a different one eventually but it works pretty good at keeping the humidity and temps up. However again a more experienced person could help out with that as i dont know how good it would be for eggs yet.