How many graduate credit hours are generally required teach in a department? I've heard some conflicting reports on this, but in general, how many graduate credit hours are required to teach in a department or secure a professorship in it? 

I'm an interdisciplinary PhD student with a heavy focus on computer science, but I will have close to thirty credit hours in social sciences when I'm done and I'd like to know if it is worth getting the count up a bit.
In the US there isn't a standard requirement. 

If you have a PhD, you could potentially become a professor. If you have a master's, you could potentially be an adjunct or instructor. 

Although, I have seen smaller schools and community colleges advertising a requirement of X graduate credits to be an adjunct, where X is rather small (e.g., 6 classes).