Have you discussed this with your GF? You might find that she thinks you wise to consider the possibilities, too. Does she want you to move so far away? Discuss your concerns with her before you assume how she is going to feel. I think you are wise to consider the possibilities, too.

When we have a mental illness it is always wise to consider how stress is going to affect us. I'm glad you have a therapist to discuss this with. I would make a list of the pros and cons and discuss it with your GF. Take it slow and don't do something just because of money. It's not everything. Quality of life means more.