A single failure is often a company's downfall. Never take on something you cannot handle. If you know the job is beyond your capacity, then recommend another artist immediately! Even if you can not do the job, the (professional) recommendation can be a success. You need to know artists that are accomplished in their medium, such as calligraphy, printmaking, oil paint, acrylic paint, colored pencil, photography, pottery, etc. A network of artists that support each other is essential. Always be connected to other professionals in your field that can take on jobs that you can not facilitate or do not want to do. You will retain integrity and maintain respect for recommending a suitable alternative. If you have the theory that "failure is not an option," you'll never fall into the "unprofessional" category. It's always more important that the customer get what they want than to compromise your field of expertise. I would much rather a client say, "he couldn't get to it right now, but he recommended so and so and they did a fantastic job" than "he said he couldn't do it". After all, if one artist recommends another, then we all win. Networking is what it's all about. The links to the right of this page are good examples. These are people I would recommend to you, and I suggest you do the same.