I am a Canadian living in Miami, I just received my PHD, been living in the US for 6 years. I need a greencard now. How long would it take? and $?

The processing time and costs will depend upon which employment-based category you intend to pursue. The process could take anywhere from 6 to 12 months assuming you qualify for either EB-1 or EB-2 classification. Having a PhD alone is not simufficuebt to obtain a green card. There will be other requirements that must be met. You may be required to have an employer sponsor you. You may be required to show exceptional or extraordinary ability. You can read more about employment immigration at http://myattorneyusa.com/employment-immigration.