New or used, whichever you choose I'm sure you'll be happy. I jumped from a big house into fulltiming in a 22 ft CCD about 2 and a half years ago. A year later I surrendered to the need for more space and went to a 25 FB SE.
Advice - look at lots of actual Airstreams before you choose. Things that irritate most - bed size and bathroom size. Some bathrooms (esp those right next to a "full bed") require a very tight squeeze to get into, and if you're married, crawling out over each other is a big issue with the full bed. 25 ft and up models have a separate bedroom and the choice or a queen or twin.
Find the Airstream FIRST, then look for the right tow vehicle.
Decide how much work you want to invest in before buying vintage - you can find lots of 1, 2, or 3 year old units that are really "as good as new" but if you're buying something 10+ years old, expect to replace some appliances and do some repairs before it's fully safe and roadworthy.
Check for rallies in your area - people love to show off their units and find a dealer with a generous inventory. The best dealer in terms of stock on the east coast is probably Colonial Airstream in NJ. Colonial Airstream " Of New Jersey " 1121 Rt. 88 Lakewood, NJ 08701 Airstreams #1 Volume Dealership
Of course the classified ads on this site are a great resource too.