Dear {House Sitter},
A heartfelt thank you for looking after my home and {companion animal(s)} while I was gone. I couldn't have picked a better person for the job.
You treated my house with utmost respect, as if it were your own. I think it's actually in better condition now than it was before I left! You also took really good care of my beloved {companion animal(s)}. It was hard not being with {him/her/them} for {several/so many} {days/weeks/months}, so I truly appreciate the daily {photos/videos/video calls}.
Thank you for being such an amazing house sitter. I will definitely recommend your service to my friends and family.
Sincerely,
{Your Name}