Dirty Rotten Thieves

[Steve Sparks]

So it seems that once every few months someone gets into one of my houses and steals something. Usually copper but I just had $400 in plumbung supplies taken. Any ideas on cost effective ways to try to prevent this? I am considering just getting the phone lines turned on to get alarm systems in place. Seems like it will be like $40 per month per property. Any other ideas?