Well I don't have a dedicated business as such but the tool that works for me in terms of the accounts management, invoicing and billing is Replicon. The cloud based platform with user friendly and calender based interface makes it effective all the way to give the desired end result.
One such software I have been using for my professional as well as my personal task management. I think so that it will work out for you as well. The tool that I am talking about is the cloud based task management tools from Replicon. Here is the link for your reference -...