What you are actually buying: the account, the app, or the link between them
An account sold with an app is three separate things: the account's entity and standing, the app's ownership and release history, and the binding between the two. On Google Play a package name cannot be changed after publishing, and an app lives under the developer account that created it. If you want to keep shipping updates to that app, you are in practice taking over the whole account, so you are evaluating the account's entire history, not just one listing.
Check the real app status in the console, not a store-page screenshot
Ask to verify console-level state. The fields that matter: whether the app is published, unpublished or only in internal testing; the date of the last production release; any policy warnings, violation notices or rejections; and whether the target API level meets what Google Play currently requires for new releases and updates. An app that has gone stale may be blocked on its first update, and the engineering work to fix that can cost more than the account. Exact requirements are defined by Google Play's current policy pages.
Package name, signing and source code decide whether you can keep updating
Updatability comes down to signing and source. Confirm whether Play App Signing is enabled and whether the upload key can be reset or held by the new owner. A legacy self-managed signing key that has been lost makes updates very hard. Also confirm you can get the source, build configuration and the third-party SDK accounts for ads, analytics, push and login. Without source, a with-app account is only usable as an account, not as a product you can maintain. That distinction should be settled before payment.
The app must be consistent with the account entity
Developer name, privacy policy, support email and the Data safety form should line up with the account entity. Personal and organization accounts differ in verification requirements, public-facing details and liability, and organization accounts involve entity data such as a D-U-N-S number. If the entity shown in the app does not match the console account, later updates or appeals can trigger additional verification. The personal-versus-organization trade-off is covered separately; here the question is whether the app and entity are coherent.
Monetized apps need one more layer of checks
If the app has paid downloads, subscriptions or in-app purchases, payment profile, tax details and the merchant account come into play. These are tied to the original holder's identity, so you need to know whether they can be changed and what that does to existing subscribers and payouts. Also check for unsettled balances or open refund disputes. Anything involving money should be written into the delivery scope as included or excluded, not left as a verbal agreement.
When to stop or switch plans
Pause the order if the seller cannot show app ownership at console level, if the app has unresolved policy warnings with no explanation, if you need ongoing updates but get neither signing keys nor source, if entity details clearly contradict the app's listing, or if anyone promises the account will never be reviewed. If you only want an account with history, an aged account without an app is the cleaner choice. If you want a product you can run, assess source and signing handover first, then the account.