Never enter into a single agreement for the creation and maintenance of the site.

Just saved a man :-) More precisely, a small studio from Ukraine. Judging by the content of our conversation with them, for small start-up companies the following words will be relevant:

Never, never enter into a single agreement for the creation and maintenance of the site. In general, never under any pretext.

Filling the site should go a separate contract. Making photos and illustrations, copywriting is also better (but not always successful, alas) to enter into separate agreements. And, especially, website promotion should be a separate agreement.
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It is necessary to state in the contract for the creation of a site that content creation and content (submission to the site) is not included there. And during a conversation, make the client pay attention to this.

I suggest to guess why ;-)