Funny you bring that up. I've starting planning for a similar trip myself, though I'm going to do Asia this time since I did Europe last time.
To prepare, I'm listing all of my financial obligations that will continue even when I'm gone for a year. This includes:
- rent for a storage facility (I may sell some stuff but most I will keep as it will cost me more to re-purchase everything than to store it)
- cell phone service. i don't want to lose my number so I will either 1 - upgrade my phone to one that can be used internationally, 2 - cancel my current contract and port my number to a pay as you go plan
- web hosting.
That's pretty much it for ongoing expenses. As an alternative to storing my stuff, i could rent out my furnished apartment but i'm not too keen on letting someone else use my stuff.
so, i'll need enough in my checking account here to cover that which means that since I'm planning on going for 6-9 months I'll need about $1500 to be safe. i'll set everything up for auto-pay.
I'll want another $1500 on hand to re-establish myself once I return.
For trip expenses i've figured this trip will cost around $15k.
So, all told, to check out for this amount of time I'll need about $18-20,000.
I'll just start saving that in a regular cash account and when I get it I'll go.
Your trip will probably be more expensive since traveling in europe, even on the cheap, is at least 2-3 times more expensive than Asia (and that is REALLY traveling on the cheap). For 2 people you probably want to budget about $100/day for Europe unless you have people you can stay with or will focus mostly on eastern Europe. Unless our exchange rate goes it, it might even be more.
You are only going to have to start over if you spend what you already have. however, if you continue to save for retirement (at least the basics of matching 401k and Roths) and then save separately for this you should be fine.
The biggest things might be your jobs...it depends on what you do. I took a year off when i was 27 and changed fields when i came back so it wasn't a problem.
As far as volunteering goes, many times you have to pay them to volunteer so be aware of that.
Just do your research, run your numbers, come up with a budget and start saving.
This is a good thing you're planning on doing. I think everyone should take some time off whether they think they can or not.