You are available to work during the summer full-time
During the 12 weeks of summer internship, nothing should take precedence over your project, and you should have no major distractions. If you have another job, decide whether you prefer it or Summer of Bitcoin and pick one. If you have more than a few hours a week of extra commitments, you probably should skip participating in the program; it is unlikely that you will be successful.
You have good Internet connectivity continuously over the summer
You are able to stay in regular close contact with mentors
This could be via the usual open-source means (email, chat, Jitsi etc) for the duration of the summer. It is not necessary that you be geographically near your mentor.