What percentage of the profit to pay the programmer / developer of the site?

Question

Fintech

There is a good friend of a programmer who deals with exactly the topic that interested me for more than 5 years, but I could not find the artist. He agreed to make me a site three times cheaper than other developers offered me. The main difference from the rest is the presence of a parser, which they have been developing for a long time, I agreed to rent 4 times cheaper than analogues, the functionality is also 10 times better than analogues. I understand that I will be completely dependent on the developer, because without a parser the whole site will not work and it will be necessary to change the code and integrate a new API provider, and this is time and money.
The site is almost ready, but in a conversation about how I will pay for project support, we started talking about interest on profits. In principle, I don’t mind motivating the guys and improving the project, since I plan to do three times more than at this stage, but how much of the site’s income should I pay it if I fully pay for promotion and sales, also pay for the work of moderators. In general, how much to pay a programmer for project support? For revision, I understand that I will pay for hours, but if I pay a percentage of sales, then why should I pay for revision?
I'm not really pulling the budget, I can barely manage the promotion, so I thought that the percentage of sales would be beneficial for both of us.

Answer 1

The percentage of sales for a programmer makes sense if he will also sell. Directly or indirectly. If you cannot make a connection between the work of a programmer and sales, then you pay a fixed price. Moreover, the connection must be significant, which is difficult to imagine if the rprogrammer only programs, and does not deal with calls, or some other promotion. sales = effort * k. This "k" is the percentage of sales for his contribution.

Answer 2

You can always hire another performer to support (if this developer is honest and does not destroy what was created).
So this percentage is just the result of an agreement between you. Usually it is in the range from 0 to 100% - as agreed.

Answer 3

That is, the whole business is the parser. And the idea is also not the author's.
In this case, it is difficult to talk about a startup or about any business in general. In fact, the author acts here as a seller of someone else's product (the result of parsing), investing only in promotion.
What percentage to pay a programmer who already has this parser - how to negotiate with him.