I have a second home that I am selling. My broker tells me she's noticed the water in the toilet in the master bedroom is slowly flowing over the flush tube. My question is if this doesn't get fixed, will it run up my water bill? Any help is appreciated.

Yes, it will. It is running water. It's not a difficult fix at all.

Yep, and cost a lot too. Adjust the float arm or have someone help you do it.