simple_girl and others who have used house sitting services (housecarers.com or trustedhouesitters.com) - do you have security cameras in common areas in your home? DH is VERY concerned about a stranger staying in our place, but we have hopes and plans to travel overseas or without the fur-kids for extended periods of time (2-8 weeks). Did you require the house sitter to get renters insurance?
We do not have security cameras inside or outside of our home, BUT, I think it is a great idea, especially for entering/leaving. This way you could tell if the sitters are staying with your pets a reasonable time and also if you have a dog they are walking that they are doing it regularly. In addition you could make sure that they are not bringing others into the home (except for those you have approved of, of course). If we still had pets and needed a sitter, I would get security cameras put on all doors and make sure the sitter was aware that we would be monitoring them from afar.
We lived in a townhome when we used sitters. We were close friends with our next door neighbors and made sure to introduce the sitter to them and make it be known that they would be keeping an eye on things (and also if they had any issues to contact our neighbor for help). We would periodically check with our neighbor who would let us know if the sitter was there as expected, doing anything unexpected, etc.
We also told our sitter we expected regular texts with pictures of our pet - this gave us a great feeling of security.
You can also lock off a room of your home with things you don't want disturbed if that is of concern to you. I made very sure all of our financial files were locked in a safe as well as any prescription drugs, etc. We don't have valuable items in our house, but if we did, I would store them in a locked area just to be extra safe.
I also did a very good job of screening via talking to the sitter's references and interviewing the potential sitter. We used Skype or something similar. Also, trusted housesitters has online references/reviews from past homeowners - I would use someone who has at least several good reviews. I would also ask to talk to at least a few of their references to make sure I wasn't missing something left unsaid in a review. In addition, you might want them to have the criminal background check service done via the Trusted Housesitter's service. We did this for potential homeowners to give them an extra feeling of security.
You can set up a contract with the sitter if that makes you feel better - we didn't - but I did consider it. You could ask for a bond as well; I've not done that but if a homeowner asked me I would consider it to give them peace of mind (depending on how much it was/how it works - haven't done that before). I don't know how renters insurance would work in this situation - you are afraid of being liable for something of theirs that gets destroyed?
There's always some unknown risk (so it's not for everyone), but I really like the trustedhousesitters site because homeowners can leave reviews of sitters, and likewise. Sitters are more likely to be on their best behavior if they want a good recommendation. One bad recommendation can tarnish your ability to sit from there on out. So that feature on their website helps me feel more secure.