7 yr old rescued lab

Question
Hi. We rescued a l yr old lab 6 years ago. He was found homeless, starving and with mange.  Now he is a 100 lb big guy and a fantastic family pet.  We also have a 3 yr old labradoodle we have had since she was a puppy. Ben, the lab, is definitely dominant over the female.
My concern is the aggressive behaviour that seems to be worsening in Ben.  When let out into the yard, he charges any people or animals walking by.  When someone comes to the door, he lunges at our guests -- but more frequently, as a guest is leaving he lunges at them from behind and tries to bite them.  Furthermore, for the last 6 months or so, he has begun urinating on our carpet of our bedrooms --sometimes even as soon as 5 minutes from being let outside to relieve himself. We are getting ready to spend thousands of dollars to put up a fence to protect our neighbors from Sam -- and also protect our liability in case he were to bite someone... he has come close many, many times.  Currently we have an electrical fence that is very effective -- unless a person or dog is walking by - at which point, he charges through the fence.  Can you help please? Is this an owner problem? or a breeding problem?  We love this animal but are at wits end.  He is becoming very expensive -- yet much more aggressive and we don't know what to do.  The urinating on the carpet is perplexing and gross.  Please help!

Answer
First it may be a health problem,such as hypothyroidism which is hormonal and can cause sudden changes in behavior and also urination,so it won't hurt to check that first

Second if this is behavioral this is a very serious problem and I think the best way to solve is to call around and find a trainer that can come to the house and see the problems you are having with this dog-a trainer can really work wonders on dogs and turn them around and that is the best way as they can show you how to correct problems,and in a case that is as serious as this,I think a trainer is your only option

As for the cause,you may never know if it isn't medical-it is most likely a combination of several things