I have currently finished my master degree and I am working 20 hours per week. I have talked to several professors in my field of interest and they said that the earliest position for a PhD would be in december, because of funding.

However, I think I could take the route as external researcher and do my PhD by working 20 hours per week and devoting the other 20 hours to my research.

By browsing some posts here I have read that a lot of you consider an external PhD as inefficient, like it takes a looooonnnngg time ect. . Why? What are the reasons for that? Can`t such a PhD not be done during 3 years?

I appreciate your answer!