I was thinking about rentals for a month or so in each place. I'm interested in Germany and Austria, plus places along the Mediterranean in France, Italy or Spain. I'm thinking about doing annual trips to Europe in the summers where we might stay in two or three places as "home bases" and explore areas around there. I do realize there is the 90 day Schengen law, so probably no more than 90 days at once.
Airbnb does look pretty good, but often the ads on Craigslist for at least Munich and Vienna looked really nice price wise, and some did say they were available for a month.