hw do i get around a apple activation lock when its someone selses iphone4?

The previous owner needs to go to https://www.icloud.com/find/ and erase the device, then remove it from their account. If they won't do that, the device is useless. Apple won't unlock it.

Turn off Activation Lock - Apple Support.   *

Ask the seller to remove the lock or give you a refund. It's an anti-theft measure.

That iPhone was likely cheap because the seller wasn't able to use it; in this case, you won't be able to use it either. If it seems too good to be true, it probably is.

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