Tim’s got this bang on. Splitting it into 5 makes no sense. And paying to join a band? Absolutely insane.
If the band is successful enough to generate a substantial income, you can set it up as a business. We did this when I was in a signed band. We actually took out a loan to pay for assets and recording and paid back from profits. There was no requirement for a new member to pay us.
Also, you have to consider what happens if you treat it as a business. Do you all contribute equally?
The person driving the van, booking the gigs, storing the PA and managing the social media can all legitimately state they’re doing more. Do they earn more?
Socialism may not work in the real world, but the principles apply here.