Non EU in Italy

Purchase taxes are the same whether you are an EU or a non-EU citizen. 

Plus being an Italian resident has disadvantages, not only advantages, if you don't actually live in Italy. Especially, as I am understanding from posts on this forum, re taxation and charges levied on overseas income and assets. Could be short term gain but long term pain. Do your research thoroughly. I add that I am no expert and could be wrong on this but it doesn't look that advantageous in the long term to me to chase this particular 'loophole'. 

Okay, it is news to me that the channel islands are ex UE. However, as ex UE, you need a permesso di soggiorno (which will, in the first instance)l last for 90 days (we are taliking theoretical here). But as Gala has said, there is nothing taxation wise to deter you from buying a house here, and bizarrely, if you chose to take up residence, there are some adantages in being ex UE. In my experience, folk who domicile themselves in the channel islands are not short of a bob or two: and if you are ex UE you fall into the same category as hard working Moroccans - and my inclination is to assist these north africans before I can be bothered to consider the trivial taxation implications of a channel island resident.