I want to buy a second hand iPhone 4, but how would I know if it's iCloud locked or not?

I want to buy a second hand iPhone 4, but how would I know if it's iCloud locked or not?

I don't recommend you get the 4, you should get the 4s at least; but well now to your question, you'd need to go to settings/iCloud and check if where it says find my iPhone is on or even if the account is activated on it. If they restored it, after you set up everything in the hello screen it shouldn't ask you to sign in to your iCloud account or connect it to iTunes, it should just go to the homescreen or ask you to either sign in to an existing account, create a new account or skip that step, but not forcibly need to sign in to a specific account to activate it.

If who sales it tell you he'll give you the password later because he forgot it, it's a scam, but since it's the iPhone 4, there's a way to bypass the iCloud activation. You can only bypass it on the 4.

Try going through the initial set up process. Eventually, if it is iCloud locked, you should come to the screen showing that. If not, then you should be good to go.