We are landing in Munich and need to take the train to Passau. Should we buy our train tickets in advance, or can we buy them when we get to the airport? I'm assuming there is a train station at the airport? We are new to this as we usually rent a car. Thanks for your help :)
If you take regional trains there is no need to buy tickets in advance. The most economical solution is the Bayern ticket (€34/2, valid after 9am on work days and all day on weekends and public holidays). Buy it either from a vending machine or (with a service charge of €2) at the ticket window in the Airport Center. There are no direct trains from the airport to Passau. You can take either the bus to the nearby station of Freising and transfer to a train to Passau or take the train from the airport to Landshut and catch the Passau train there. Those trains leave the airport every hour at min. 28.
All details at www.bahn.com.
There's generally no deadline to buy a train ticket in Europe. And since Germany's trains tend not to require seat assignments, there's less reason for advance booking there than in countries such as France. Longer-distance trains InterCity and InterCityExpress trains can be cheaper when booked ahead, but that's not terribly relevant to the route you're traveling.