Why can't you bring someone to the table that knows the sign biz? Seems like the logical thing to do. Otherwise you're going to expect people to pay you to make signs when you don't know how to do it. For example, just because someone can draw doesn't mean I would pay them to put a tattoo on me when they've never done it before. There's more to it than design and software. You have to know the different materials available and when to use them, how to lay vinyl, how to answer people's questions and so much more. An online message board isn't the place to learn all the stuff you need to know to open a sign business. I'm not saying you shouldn't start your biz; just trying to give you advice so you'll have a better chance of succeeding.
Here's an example. What if I go to a forum for professional graphic designers and posted this: "I've been in the sign biz 20 years but now I want to focus solely on graphic design and start my own graphic design business. I've never worked for a design company so maybe you guys can help me learn along the way the business end of it." I think I would get slammed and laughed at. Neither of which I want to do to you. I want to encourage you to get knowledge and experience before jumping into something you don't know much about.