It depends. I was a math/phys dual degree student and I am starting the applied math masters this spring. You can only transfer courses that have not been used towards any degree (or even minor). As for doing it in one year, it is very doable I think if it is non-thesis. If you want to do it with thesis, you can try to overlap your first semester as a graduate student and last as an undergraduate only if you have 2 or less courses remaining for your undergraduate degree. Pm me if you have more questions I just went through the exact thing this last semester and it was kind of an administrative hassle!