For whichever city you saw the 1 euro homes advertised (there are several), try googling that city’s government website.
Cinquefrondi is just one of the many Italian town’s advertising this incentive.
Depending on what country you’re from, the official government website for that small Italian town may require some digging. Try to search through the first three pages of Google.
Different towns will have their own ways of communication. For example, Cinquefrondi has a special email for inquiries. They have many requests coming through, so just be patient and they will get back to you after you’ve reached out to them. Click the next ARROW to see the next page!