Well, firstly did you book your flights already? You can save quite good money if you know how, i have been in most of northern European countries but not rome neither Barcelona. Yes i tried air bnb alot and its not always good way to save money, as owners got used to hide some info so read reviews very carefully and choose a place with good rate, i suggest you better book from booking a private flat or hotels where they are not near to center in any city but with good rate too, yes you will have to walk or use transportation abit but isnt this part of any trip. However, in my opinion, to save money is to be flexible in traveling dates and flights generally which the most important, if you did it right you can have your stay in good place easily where the difference will not be that big.
