Hi, welcome to the forum, and good luck with your search. There are strongly held opinions on both of your questions.
2 axles v. 1
Pro - with two axles you can have more margin for weight with axles and tires, a single tire failure is not totally disabling - you can tow short distances at reduced speeds with one tire on one side.
Con - with two axles there is more stress on tires when turning, there are more tires to maintain and replace.
Regarding new v. used - you can read the threads on here about build quality and problems. Don't let it overwhelm you, people seldom write in to say how great their trailer is, but some do.
Considerations if buying used:
1. If you get a gently used and well maintained used trailer, the previous owner(s) will have worked out all the bugs, but when a problem does happen, its going to be on your nickel.
2. Someone else ate the depreciation.
3. If you use it a while and decide you absolutely have to have something else, you will be out way less money when you trade.
4. There is a wealth of information on here about DIY repairs if you are the DIY type. Most things are not rocket science. If you are reasonably handy with tools and have done some auto maintenance, the Airstream should be within your skill set.
Considerations if buying new:
1. Everything will be under some kind of warranty for some period of time. They won't all be the same - appliances and some, if not all, accessories are covered by their manufacturers.
2. If you plan to buy from a dealer near you with a good service reputation, that could weigh in for the new trailer. If you don't have a nearby dealer, or if the ones nearby don't have good reputations, the warranty may not be worth much. You could have to drive a day or more, leave the trailer, come back and pick it up.
3. You will probably take a significant hit for depreciation if you trade in a few years. While Airstreams hold their value very well over the ling run, the first few years are tough.
4. It will be NEW! You will be the first person to use it. This is good and bad; you will be the first person to sleep in the beds, use the shower, etc. but the first dent or scratch can be traumatic if you are concerned about those things.
Good luck with your choice and enjoy whatever you decide upon.
“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins