Welcome to the forums! This the place to find all things Airstream!
Lots to consider ~ just reading through the threads here can take you years... but so much good information. Try the search function it can help. But try for specific searches, like Safari, etc.
You might check out and see if there is an Airstream rally somewhere near you before long. Going to a rally and dropping in can help answer questions! Lots of times folks will give you the "low-down" on their size camper, etc. All the pros and cons will be discussed! Besides you get a chance to see lots of makes and models.
Here is a thread that covers quite a variety of information. http://www.airforums.com/forum...eam-22920.html
You not only want to see what size you need, but what layout, what year range, amenities, etc. Depending on what you like to do for camping... some state parks and National parks have size restrictions.
What to look for: The biggest factor is a soft floor. Floor rot will be there if it is over 20 years and often much less than that. Also if over 20 years old the electrical wiring might not serve your needs especially with a family... it really helps if you or your Mrs. is handy with tools.
Have fun surfing the forum. You will find lots of answers!
Mrs. NorCal Bambi (traveling in S Tardis)