Sounds like youve found a good trajectory. I am in no way a CNC GURU, we are only a year in to CNC in the shop but different from a 2K machine we were in for 75K total investment (50K on the CNC). My only input based on your response above is that other than custom carving on a panel (chaff's of wheat, custom carving, etc) a CNC is going to do you no good with regards to cabinet doors. Even cathedral arch, roman arch, and so on, can be done far faster non-cnc. Now if your guy has a demand for personalization or completely custom 3d carved panels on a cabinet door, and the customers to pay for it, then thats a nice market.
One off sign work, unless your in an affluent area, is very difficult in my opinion. As Kieth mentioned, you have multiple sit downs/back and forths with the customer over design, size, budget. And in the end when you whack them with a $500 price tag (3 hours of talking and design at $60 an hour, 3 hours of run time (singe sided), material costs, and painting and finishing) they are like "oh, I just wanted an ol' sign to hang on my stoop". Around here people are thinking of the routed signs you get at the fair where you tell the guy what you want on the sign and he is a proficient free-hand router and he blasts out a sign on a piece of pine, torches the letters, sands it, and ships you off for 40 bucks.