Well I can tell you that Castle rock or anywhere else in Douglas county is going to be expensive. They have the highest income tax bracket in the state and one of the highest in the US.

As for vehicle registration. I was paying about 350 bucks to register my 06 F150, but im sure its lower since then. I would check the Colorado DMV website to see if they have information on that. It is based on vehicles value. Keep in mind also you will need to get emissions testing if you move within certain areas of the metropolitan region.

Wish I could help you more.