The problem with VRBO which we have used and are using again this fall in France is that it is essentially the classifieds; your experience depends on the integrity of your landlord and you have to do your own due diligence. So triangulate; look for independent reviews; talk to the landlord on the phone; learn to read photos and descriptions carefully. Make sure you have photos of everything important to you. If they claim a terrace, make sure you see pictures; if you don't it will be where broken bicycles and garden furniture is stored or it will overlook a dumpster. If you don't see the bed, it will be small. If there are tons of arty closeups but no good wide shots that really show the room, there is a reason. I found a place in Paris that was in an area I wanted and looked really great with a charming garden and also an adjacent garden room for dining. Looked great. The reviews said things like 'the garden is full of trash and used for junk storage and is totally unusable' and the owner is an artist who just leaves half painted canvases, paint buckets and materials and junk all over the house making it hazardous to even walk across the room' among other delights.
One site I have found useful for reviews that are independent and by following up I have found a couple of really spectacular places is the slowtrav.com site. They run reviews of apartments and the link for the apartment is there if you find any of the reviews appealing. We found our favorite apartment in Italy there.
I have also used AirBNB but not in Italy. We have lots of friends who love AirBNB and use it and we have had some experiences with it although not in Italy. The consensus among my friends is that those places are much more of a gamble i.e. dirty places or places without good maintenance seem more common.
Often places are listed in more than one site and if you use a bit of the descriptive text and then 'reviews' in a search, you can uncover listings on more than one site and sometimes for less on some than others. It is also a way to get reviews. It is critical to discover if the particular landlord has a bad reputation as that is everything. Look particularly for people who had their trip cancelled for 'water damage' or other often bogus reasons. (water damage or plumbing problems is the code for 'we rented it for more to someone else after committing to you'. )