If you are talking about becoming a professional dog walker, then I guess you are just starting out being a dog walker for the first time? Since you are asking about leashes for more than one dog.
I cannot see anything about the leash from that photo. All it shows is the tag, so there is no way to tell what structure it has.
If all you mean is you are going to walk your own family's dogs, then that's different. But if you are meaning walking other people's dogs then you would do best to research all about it very thoroughly before you take that on. Dog walking, if indeed you have not ever done it before, is more complicated and tricky than you might think. It's not just about getting the right leash. There are legal ramifications for you and/or your family if a dog belonging to someone else gets harmed while you are walking them. And much more. Insurance will be required. Just speaking a word of caution.