Two questions hide inside 'is it reliable'
One is whether the account can be fully handed over to you. The other is whether the app inside it can keep shipping updates without interruption. Apple offers app transfer in App Store Connect, which moves an app from one developer account to another under conditions published in Apple's documentation at the time. The alternative is a full account handover, where the seller passes over the account and its app together. The risks differ between the two, so confirm which route the seller means before checking anything else.
Check 1: confirm app status in the backend, not only on the storefront
A store link proves the app was listed at some point. It does not show which account owns it today or what state it is in. Ask to verify the Bundle ID, SKU, current version status and version history on the app information page in App Store Connect. Look at three things: whether the app is still available for download, how long it has gone without an update, and whether the review history shows repeated rejections or a past removal. An app untouched for years can hit new SDK or privacy requirements on its next submission.
Check 2: the seller name and account type must fit your plan
On an aged account with an app, the seller name on the store page is public. Individual accounts usually show a personal name, and organization accounts show the company entity. If you plan to operate under your own brand, find out whether the account is individual or organization, which country or region it was registered in, and whether the displayed name can be changed through Apple's process. Whether a change triggers re-verification is governed by Apple's current pages, not by what a seller tells you. An old account that mismatches your purpose is the wrong account.
Check 3: will the Apple services the app relies on survive the move
A live app often depends on in-app purchases and subscriptions, push certificates or keys, Sign in with Apple, iCloud containers, associated domains and app groups. Under app transfer, some of these need extra steps or carry restrictions, as Apple's transfer documentation describes. A full account handover keeps the original Team ID, so these dependencies stay more intact. The practical test is to ask the seller for the list of enabled capabilities and confirm each one against your chosen route. If the seller cannot produce the list, they may not understand what they are handing over.
Check 4: credentials, trusted devices and holder rights must transfer cleanly
Ownership in practice means control. Verify the Apple ID email, phone number, two-factor trusted devices or numbers, and the Account Holder role. After handover you should be able to sign in, change the password and replace trusted numbers on your own, with no recovery path left in the seller's hands. If the seller wants to keep control of any email, number or device, stop. That arrangement means the account can be reclaimed or hit with a security challenge at any time.
Check 5: servers, source code and third-party accounts need to be spelled out
A live app is not the same as a maintainable app. The backend, domains, privacy policy and support page hosting, and the keys for third-party SDKs such as push or analytics all decide whether your next update ships. A useful test: could you build and submit an update without any help from the seller? If not, write source code, backend and third-party account delivery into the order requirements. If any of these five items cannot be confirmed in writing, pause payment. Fayar sorts Apple developer accounts by country, individual or organization, and whether an app is included, so this list can go straight into your order brief.