This is a "My Guy Syndrome" question. Our page for My Guy Syndrome is pretty good and is worth reading.
Briefly: roleplaying is a tool for having fun, and if your roleplaying is causing you to not have fun, you shouldn't do it (or should do it differently).
Also: you're using phrases like "my character wants X" but remember that you are deciding what your character wants, and you can choose to decide differently.
If you really want to tell a story where your character buys a tavern, you could tell your DM that your character is buying a tavern and spending a few days taking care of it, and then leaving to go back to adventuring, but he'll come back for it after the adventure is over.
Or, you could tell a story where your character buys a tavern and quits adventuring, so he leaves the group and is now an NPC. Then you tell the DM that you're bringing in a new character who will take your old character's place in the group. Most DMs will let you do this at the same experience level and (usually) with the same wealth that your old character had. If your two characters are friends, you could narrate that your old character gives the new one some of their old equipment since the old one doesn't need it any more.
If neither of these feels correct to you, I recommend you decide that your character wants to do the adventure after all.