I guess it's how the posting was worded:
I will pay for everything and we will share the money together for the 5 first clients. Then we can move on from there.
To me, this implies that you would split funds for the first 5 clients, and then "move on" meaning separate paths, and the partner would only receive the split money.
As Romes mentioned, 5 clients and then hire staff likely would not be enough to operate a business (unless you're dealing with dedicated servers, and your 5 clients are spending $150 etc). Also, I take it that by staff, you're hiring per ticket type staff?
I think a more serious look needs to be given to what it is that you want to do and how you want to accomplish it. I'm all for someone starting a business and needing a partner to get started, but if you're requesting through a forum, a more detailed plan needs to be laid out.