I know a buy-to-letter who steals books and ornaments regularly from the flats she views - she pre-plans and goes back for what she wanted to nick.
Example: She'd visit the property, catch sight of something she liked the look of in a bookshelf or on a shelf, then call the estate agent and ask 'to borrow the keys for five minutes to check pipes out, no need to bother the owners'.
Brings a rucksack to fill. She claims lots of landlords do it. Not so sure about that.