Ownership has three separate parts and a business can have one without the others. There is the copyright to the work itself, meaning the design, the code, and the writing. There is control of the accounts the work lives in: the domain registration, the hosting, the analytics property, the advertising accounts, the business profile. And there is the ability to actually use what you hold, which means having the files, the credentials, and enough documentation that somebody else could pick it up. A provider can hand you a perfect website while keeping the domain in their account, and you would own something you cannot move.
The common traps are worth naming plainly, because most of them are not malicious. Domains registered under an agency account rather than yours. Analytics and advertising accounts created under a provider profile, so the historical data leaves when they do. Websites built on a proprietary platform that only that company can host, which is not really ownership but a lease. Content licensed rather than transferred, which is the same trap a weak contractor agreement creates. And design files that were never delivered, so the next person rebuilds from a screenshot. Each of these turns a normal ending into a negotiation.
The way to avoid all of it is to ask before signing rather than after. Who will the domain be registered to. Whose account will the analytics and ad properties live under. Will I receive the source files, and in what format. Can this site be hosted anywhere or only with you. If we stop working together, what exactly do I take with me and how long does that take. A provider who is comfortable with these answers will give them immediately. Hesitation on the last one is the signal that matters.
Our position is that all of it is yours from the start rather than transferred at the end, which is a meaningful difference. Accounts get created in your name with you as the owner and us granted access, so removing us is a permissions change rather than a migration. Files are delivered as we go. The site is built to run anywhere. And if the engagement ends, nothing has to be handed over because nothing was ever held. That is not generosity, it is how a first year business avoids becoming dependent on any single provider, including this one.