You'll finish with: Everyone gets the same rules.
Five people prompting five different ways produces five different-sounding businesses. A shared project fixes that without anyone being trained.
Where consistency comes from
Put the four hard limits in the shared instructions. New staff inherit them without a conversation — and the person most likely to send something they shouldn't is the one who started on Monday.
One owner. Shared instructions edited by five people become contradictory in a month, and contradictions make Claude pick at random. One person edits, everyone else suggests.
Two people ask for the same thing separately and get answers that sound like the same business.
On your own? Ask the same question in two fresh chats yourself. They should agree on price, on tone, and on what you don't do. Where they disagree is where your instructions are vague.
If the two answers differ on a price, the offers file isn't being read — check it's attached to the project, not just sitting on your computer. If they differ on tone, your voice rules are describing a feeling rather than a rule: "professional but friendly" cannot be followed, "no exclamation marks, use contractions" can.
Sharing a project with other people needs a Team or Enterprise plan. On Pro you can still build all of this — you just can't hand it to someone else yet.