Speaking for myself, I wouldn't. Plastic is going to be hard to clean, and unless white or transparent, as hard or harder to tell it
needs cleaning. Also, unless thick and/or high quality, it's going to be prone to warping or cracking potentially, and you'll likely need to reinforce it with a brace or a frame of some kind just to keep the sides from bowing outward.
By the time you'd spent $25 on a cheap 40g tote, or $57 on a quality plastic tub, you not all THAT far off from rimmed 40g breeder for $75 on sale right now at PetCo. Especially if you were going to use a tub, it doesn't need to be an expensive rimless display tank made from ultra-low iron glass. And if you watch the forums here long enough (and maybe facebook marketplace), you can almost assuredly find a 40b cheaper than that, if you're patient.
Tubs are fine for cooking rock in, where you're going to put it with a heater and a pump and forget about it. But as a grow-out tank, it's less than ideal unless extremely shallow and wide/long. Even then, you're kinda going beyond plastic tub and into pvc or fiberglass troughs... which are NOT cheap.

(Pic yoinked from Reef2Reef user Sangheili - that fiberglass trough cost several hundred dollars, to be sure)
Also, you don't really want to have to switch things up midstream, or you're going to be resetting yourself just as you've gotten moving forward. You don't have to do all the things exactly the way you'd like long-term from the start, but you know the old adage, "If you want to make money, you have to spend money." If you know your goal is to raise frags for sale, maybe modularize your planned/goal setup as much as possible, if eventual expansion is the goal, but, yeah.
I'm sure more than a few people do/have-done it, but seriously, I wouldn't. From my perspective you're just kinda asking for all sorts of trouble, long term. that could be saved by investing a little bit more upfront to start off the right way. Given what you're going to need to spend on lights regardless, a 40b is a pretty inconsequential expense, and a good starting point - not too big, not so small that you won't have plenty of room for frags.