By Mike Sullivan, WBZ-TVWALTHAM -- It's a growing trend that the Better Business Bureau (BBB) expects to get worse when college students return in September. We are talking about rental scams. "A living nightmare is the way I describe it," says Ashley Colindres, a Waltham resident looking for a new place. "They will all ask you to send money up front, tell you that you can go look in the windows to see if you like the place. If you're still interested send us a deposit, and we will mail you the key."So far, the BBB says 12 people have...