If I understand correctly you are considering a *NEW* Airstream? Why not buy someone's almost perfect "used" one and save fifty thousand dollars. That would take care of a lot of cushion. Or a hundred plus thousand if you are going to finance it? Don't buy a fixer-upper or a "vintage" project but one someone else has fixed up. Well, that's an idea, anyway. Smile. You can get SO much more house if you don't have to take the initial depreciation. Think about it and ask here for other's advice. I saw one poster on this very thread that has a 32 footer who said he wishes he had a 34 with dinette. Buy his. Offer him top dollar for it and put the 75 thou difference in savings.
Also, when it's all said and done, the hardest and most important question to answer, and the one that most people are too nice to mention directly, is what will it do to your relationship. That's the difficult thing to answer. Try it out. Go camping in bad weather. Be brutally honest with yourself/partner.
And are you thick-skinned? You can have a million bucks in the bank and have a wonderful life, but many, if not most, people who are slaves to their possessions and employment will still consider you "trailer trash." Probably some of your relatives too.
The question I asked myself was if I would regret it if I got to the end and had not tried it, but had continued to stay tied down. Still, after three years of full-timing I decided I needed a permanent base. I bought this farm where I am now on a lake between LA and TX, restored the house, spent enough on the fixings to buy two new AS's and have thoroughly enjoyed having three barns and a huge house for all the stuff I wanted to buy. Now I'm just waiting for a few more weeks to hit the road in the AS again. Will I sell the house? NO! I want to have a place to come park if I want to. If I do come back it will be in the Spring and/or Fall, and I'll park my AS at my own spot and probably still sleep in it here.
It's your life, and you just get one. (Well, as far as we know.) And the older you get, the more you will realize that it's very short.
Best of wishes whatever you decide. Remember it doesn't necessarily have to be an all or nothing sort of thing.