As the bride, you are not expected to pay for the travel costs of your out-of-town guests. However, you should provide them with accommodations. If you have just a handful of OOT guests, you can house them with friends and family (if you’re having a backyard wedding, I wouldn’t recommend keeping a bunch of people in that house). If there are several, it would be a good idea to arrange for them to stay at a hotel or inn. If you reserve a block of rooms (after you get enough RSVPs to know they will be filled) you can get a discount rate for your guests. Be sure to put all the information about the hotel with their invitation on a separate card. This should include a map or directions from the airport to the hotel, the address and name of the hotel, the dates that the rooms are reserved, and the phone number of the hotel.
Also be sure to provide transportation info to the wedding from the hotel. If there is a shuttle or special transportation that will take them to the site, make your guests aware of that. If you will be providing the transportation, let your guests know the time and location of departure from the hotel. Remember, your OOT guests will be unsure and uneasy unless accommodations have been made for them. This makes things easier on them and they will remember that you took care of them.