Get your visa allowing stay of 1 year or more. Then you can arrive on a one-way ticket. Shop consolidators for the best one-way rates to Europe.

On most roundtrip tickets, changing return date is $200+ any change in airfare.

On some student tickets, changing return date is only $75 + any change in airfare.

The airlines have different classes of tickets, and the least expensive are usually for trips that last longer than a week, but less than a month, so if you get one of these and try to change the return date to more than a month, you will have not only a steep change fee, but a higher cost for the return flight, since your trip will be over a month, and you may have to do multiple changes, incurring fees each time, as your return date is so tentative. Bummer.

You might look at student tickets, if you qualify.

If not, I think your best course of action would be to buy a less restricted ticket that allows a cost free change of the return date. These tickets do cost more, but give you the flexibility you need.

On most sites where you search for tickets, you can select nonrefundable, less restricted, or not restricted (or similar words) and try looking at the middle category to see if those fares allow a change without fee. I recently priced a domestic flight and the most restricted fare was about $375, while a less restricted fare was about $600, let us earn additional frequent flyer miles, and change the dates with no fees. Not a bad deal when you have a grandchild on the way at an uncertain date, and a coupon good for your partner’s ticket.

I seem to recall that there are a very few airlines that offer reasonably priced oneway fares (on most airlines, a oneway fare can cost far more than half of a roundtrip, some even seem to charge less for a roundtrip than for a oneway). I would look for an airline that has decent oneway prices. I have even seen situations where a person bought a roundtrip to get there, threw away the return ticket, and bought a round trip to return, again throwing away the return ticket. That violates the terms of the purchase contract, but what can you do if you are kidnapped while going to the airport, escaping only after you have missed your flight.

thanks for the help guys… looks like i have a lot of research to do!