It's hard to know without knowing (or meeting) the folks involved. I tend to be very suspicious......and I have to remind myself that everyone else is probably just as suspicious of me!

You could leave something else lying around - something that you won't mind if it gets taken - and just see if they take it. Sort of like bait. That sounds so bad but I can't think of any other way to know if they're capable of doing something like this.

On the other hand, if you're going to have strangers in your home to clean you've got to realize that they'll be going into places that the general visitor would not be accessing. So.....you've got to do some preventive care before they arrive and put away, hide or lock up anything you don't want to walk away. My only other solution is to just do the housecleaning a little bit at a time every day. That's what I do and it gives me exercise while not overwhelming me by trying to get it all done in one day.