WHEN YOU’RE just starting out in life, any old town can turn into home: the place you went to school; the place you launched your career; the place you found love or had kids or just ended up staying. Later on, though, things often get more intentional. As kids leave the nest and retirement starts to seem like a real possibility, questions arise. Where will you feel comfortable as you age? Where will you have access to good medical care, convenient transportation, work if you want it, a friendly and safe community? And where will you be able to afford to live?