If the car has been treated correctly and has not been crashed, then nothing much can go wrong, but you need to make sure the dealer has a decent reputation (might be a surprise, but not all Ferrari dealers are trustworthy...), and make sure that there is a proper warranty in the deal and I would certainly try to organise 7 year free maintenance FROM THE DATE OF PURCHASE. This last bit might be a tricky one.
But with delivery mileage, shouldn't be much of a risk and depending on price it can be a shrewd buy.
Delivery Mileage and Demo seem to be mutually exclusive. Unless I misunderstand your question, if it only has delivery miles, than it wouldn't have been used as a demo. If it has demo miles, I agree with Onno.
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