So some of the things you will want to leave at home in the care of someone mature, and responsible include: access to your blog, email and bank accounts, all passwords to social media accounts, school records,and missionsite.net. This would mean you make a spreadsheet of names, web address and passwords, then print it or save on a flash drive, or both. It needs to be given to someone responsible in case of emergency. This will help your representative communicate with extended family, or your university when you are on your way home. If ever your credit/debit card were compromised, your rep would need access to this information.
That someone should also have a notarized power-of-attorney. This document gives a person the ability to take care of legal matters for you while you are in the mission field. Issues regarding schooling, loans, credit, taxes, health care decisions, are best determined by someone who knows you. Most missionaries choose a parent. Take the document unsigned to your bank or credit union with ID and the people you have chosen to care for your legal life. They will have all parties sign it and be your witness that will notarize the signatures. Most credit unions notarize for free, some banks charge a small fee.
Disclaimer:::I can send you a blank document that we used if you comment with your email. I am not an attorney but it will give you a starting framework.