do you have a camcorder you can hide some were? you maybe could borow one from a friend or famly member? it might take a few trys to catch them but its cheaper then a servailence camra. one of my friend's dad did that a long time ago to catch a person who was stealing their mail and it worked! it also worked when some one kept vandalizing there property. he just had a cheap one that he got used at a thrift store for $10. you can hid it outside or even lay in wait with it in the house and RECORD them in the act before you confrunt them.