I am considering making a site a site that has two or more owners. What would be the best way to split the profits without dealing with a huge tax and accounting mess? Possibly setting up another adsense and affiliate account?
You have a mess already! You divide it by proportionate share between the shareholders, but run it through a single account. X, Y and Z are 1/3rd holders so each get 1/3rd income and the reporting income (the account) is reportable to all three. This, under ordinary bookkeeping, provides transparency and should be sufficient.