I get piles of once fired brass from a local range. Can't say which range, as people could get in trouble, but rest assured it's once fired.
I'd stake my life on it.
And, every time I fire one of my reloads from that brass, in effect I do.
I don't load maxed out loads, I use them solely for plinking and "play" time.
Business, IE hunting and target shooting for "money", I ONLY use brass of known origin (NEW that I bought) for safety's sake and peace of mind.
I see both sides of the coin, and respect each for their benefits and drawbacks.
But, if you choose to take that route, know what you're dealing with, the potential risks and potential rewards.
Weigh them deeply too.
The risk is yours to take or not take, based on what you know and have seen.