We have always managed to find someone in the family. Young adult grandchildren or nieces/nephews seem to be good candidates. And we do pay them a little, but know our pets, house, plants, etc are being well cared for. If you can find the right person it can work, a treat for them to have a big house to themselves, and someone you know and trust. Never been gone as long as you are talking about though.
I know this doesn't work for everybody, for us it has been hard a few times...