Thanks for your reply Brian. The answer to your question is no I have not built a box, wired it, or had to comply with UL listings before. One thing I have learned in business over the years, it never hurts to look for better and less expensive ways of doing business as long as you can offer a great product. I appreciate all of the replies so far as it helps in my education and I hate to reinvent the wheel so to speak when it comes to any part of any business. But in just the replies that I have received so far thanks to this forum, and checking with some of the companies mentioned already and having experience in fabrication and an electrician already on staff and access to people that have built signs for other companies, I figure, why not.
I'll start by designing and building a few signs for my own companies, while still using other manufacturer to supply my UL listed sign boxes for all the jobs I get in. And who knows, maybe someday, if things work out, will manufacture our own. If not, well continue to buy from outside sources. Either way, works out. Nothing ventured, nothing gained.