If you’re looking at geldings, papers won’t matter nearly as much as what the horse in front of you looks like, assuming the horse is at least 3, and by the time you’re looking to flip, he can show his reasonable potential. But something you buy as an unstarted 2yo and want to sell as a basic super green broke 3yo with w/t/c would need a known pedigree if you’re looking to sell to someone who wants reasonably upper level work.
No, you’re not likely to sell a horse with an unknown pedigree as an upper level prospect, even if he looks like he’s got the potential as a greenie, but if that’s not your market, then it’s less of a big deal.
Mares are where pedigree matters more, since some will want to be able to go the breeding route if their nice mare gets injured. But then you’re back in the “good mares with good pedigrees aren’t really in flipper territory” boat.
So it really comes down to what your audience is. You really have to have one, to know what type of horse to buy