You might look into some rental studio space in your old area, the cost is probably prohibitive, maybe if you find a retied person with a piano who can use the company and a bit of extra money, maybe $5 a session?

If they like you they won't mind going somewhere else, and it's only a 15 minute drive away. It might be a good "test" to see how good you are? Give them as much notice as possible too, they won't like sudden changes.

I fou can get them all on one day, you can offer to go to their house. It is actually a tremendous benefit to them, My guy did it and it was wonderful.

Giving them the address of the new location would be fine. :)

Hi, I'm a piano teacher who is moving house after christmas time. I built up a small pupil base, and would like to keep them if possible. I will be moving about 15 minutes drive away. What are some possible ways to either convince them to drive to my new place or to somehow teach them in the current area, for example renting out a piano room somewhere