just some questions to keep in mind:
is this a job where the person would have to update, or would they teach you how to do the updates etc.
do they have any part of an existing website (like a domain name they can use etc...)
as for the 70% 30% thing:
it all depends on the amount of money. if you were making $10 then having the creator get $3 is pretty unrealistic. if you were making $10M, then im sure the creator would be quite happy with $3M