Buying an Apple Store Gift Card from someone else at a discount, good or bad?

Hi all, I'm trying to save some money in buying a macbook pro, and have the idea of buying Apple Store Gift cards at 10% discount from other people on classifieds ads sites to pay for the laptop. For example I can buy a $1000 Apple Store Gift card for $900. This way I'll save 10% or $100.

They are willing to meet at the apple store to confirm the balance and authenticity. The card will be large denominations of $1000 or more to cover the macbook pro 15" expense. Let's say I go ahead and meet with the person, and the gift cards are all legit with the correct balance remaining. I pay them the $900 for the $1000 gift card and the transaction is complete. Now since they know the gift card codes from having used the gift card before (they made a small purchase), are they then able to go and buy something immediately on the Apple Store online using the gift card code? If so that would mean I would lose $900 cash and they get to buy something using the card they just sold me, so long as they use it before I do, and I'm left with nothing?

Is there anyway around it like getting the gift card to be put into my name so only I could use it?

Thanks in advance!