Co-sign on tenants lease

[Jenna Banaitis]

Hello:

Question:  I have a great potential tenant and his girlfriend looking to rent my apartment as he is starting his Masters at a local college. He says (I will verify) that he has plenty of money saved and his credit score is over 750. His GF is working on getting a job and will have a letter of intent to start her new job out in this area.  They are from CA; moving across country for his Masters. He will not be working while in school.  He mentioned that his parents are willing to co-sign if necessary.  How is this done? I have never done anything like this and I hate to just pass them over as all the other boxes are checked. Thanks!