The business of lying

Is there any business in lying? Sure, there's businesses that lie to you such as advertisement. What i'm talking about is when is it OKAY to lie in a business. We discussed this in our class on Wednesday and someone brought up doctors telling their patients there's hope when maybe people have died of the patients' illnesses. But, as i stated in class, that's not lying. There's always hope someone will pull through and people do it all the time. We are survivors and God is on our side.
My mom listed Realty as another possible example. After all, you can think a place looks horrible, but still tell the clients there was a lot they could do with it. Again, it's not lying. People have taken "dumps" and turned them into palaces. Thus the saying: one person's trash is another's treasure.
Honestly, I don't think there is a business where its ok to "lie", because as far as i can tell in examples similar to these you're not lying. Otherwise, you can avoid lying by dodging the question such as in this example:

Client: "Does my hair look bad?"
Stylist: "Do you like it? That's all that matters."

K~la
PS. Mom also brought up a jeweler when they say 'this ring will last forever!' when clearly the marriage won't...I'm going to leave that one alone :)