Are winter tenants / caretakers a good idea?

Hello everyone - I'm after a bit of advice...

We have a house in the centre of Carcassonne which we rent out April to October, mainly for weekly rentals to couples. We're very lucky that people take care of the house, it's very much our home from home so it would be awful if they didn't.

Anyway, the house usually sits empty over the winter and last year this caused a problem and we were very close to having our pipes burst during the icy conditions. Even though there's loads to do in town (especially at Christmas) for some reason, we just don't seem to get any winter bookings. So this year I'm going to try something new and see if I can find a couple or single person to take the house on a three month winter rental with a much reduced rent in return for them looking after the house and carrying out some maintenance jobs for us.

I've advertised this on some of the local forums but now I'm worried that there may be issues I haven't thought about - has anyone done this with their property and have any 'lessons learned' that they could share? We have a contract for people to sign when they stay for holidays, do I need something more robust for a three month rental?

Thanks in advance :-)