Tenant Screening: 2 Tenets one with good credit the other bad

[Billy Rogerson]

I am new to land lording, and found a tenet for my home in Pittsburgh last month.  At the time, she was only applying by herself, and everything checked out for her, credit, background check, etc.  Now her boyfriend would like to move in as well, but after running a background check on him, everything checks out except for his credit.  

Her credit was good enough for me to feel comfortable that she could pay the lease herself, but now that her boyfriend is hoping to move in, and he does not have good credit, I'm not sure what to do.  

Should I be concerned about his credit and not let him move in?  Or, should I have him sign the lease as well, and not be concerned?