I wouldn’t accept working for 30% as you could end up earning less than someone on minimum wage. The common split is 50/50 or 60/40 with the larger amount going to the person supplying the products and other sundry items.
However, there’s nothing to prevent a salon owner asking for 90/10 if they want to, but it’s up to the self employed person to negotiate the best deal they can get.
May I also point out that if someone wants to work on a self employed basis and struggles to negotiate a reasonable percentage split with the salon owner, then they need to look for a new salon and also seriously consider if working on a self employed basis is right for them?
When working for yourself, you need to be confident and willing to deal with any conflict that arises. There will always be tricky salon owners and clients who will try to knock you down.