Free Spirit Trophy
Leave in the RVMISSABLE
This is one of 3 endings available in the game. You can get all 3 on the same playthrough so long as you make a manual save to reload. You'll want to make a manual save at the end of the workday (before you return to the Post Office) on September 13th. You'll need to replay through that night, Sunday and Monday each time you reload it and you won't be able to skip any of the dialogue or cutscenes (unfortunately). It'll take some time for each ending but it's better than playing through the entire game 3 times.
Before you can get this ending, you'll need to get the RV. On September 6th, you'll need to deliver a letter to the Campgrounds and will meet Mickey and June, a few campers with an RV. On September 8th, you'll deliver another letter to them and June will tell you that they're moving to Canada while inviting you to hang out later in the week. Agree to hang out, then after the workday on September 10th, you'll go back to the Campsite and hang out with Mickey and June. They'll offer to give you the RV since they don't need it anymore. Agree to take it and they'll leave it at the gas station for you. When you go to pick it up, Lori will gush over the chance to do some work on it and ask for your permission to do so. Agree to let her do the work and at the open mic night, she'll tell you it's all ready to go.
On the morning of September 14th, you'll talk with Frank at the Post Office and he'll ask you if you've decided whether or not you're going to stay in Providence Oaks or leave. Tell him you're going to leave and when he asks you what your plans are, tell him you're going on a road trip. When Robert pulls you over as you're leaving, tell him you've already made up your mind and are leaving P.O. The trophy will unlock once you're back on the road and the credits start to roll.