Profit share arrangements

From time to time on this site, I've seen productions advertised as 'profit share arrangement.' Besides admiring the confidence of those advertising, my tiny mind boggles as to how one divvies up said profits. To that end, I'd love to hear from anyone who's tried this, either, succesfully, or unsuccesfully. Any advice will be gratefully received. Should anyone wish to divulge their secrets, or even, alternative suggestions, I'm all ears. My email address is johnnygrim@optusnet.com.au cheers Johnny Grim