Minimum Documentation I Should Get from a Co-Signer?

[Tricia O'Brien]

I have 3 roommates (all in their early twenties) who have applied to rent my house.  Two are recent college graduates and have okay jobs. The other is still in college and only makes about $7,000 per year plus has student loans. The one who is the student offered that her Dad could be a co-signer.  

What do you think is the minimum documentation I should require from the co-signer to move forward?  Is it enough if he gives me a copy of his driver's license and 3 month's of paystubs to verify his address and his identity and current income? Or should I require he pay the $55 fee and do a formal application with credit check, eviction  history, and criminal background check?  

The two who are working full time (and not going to school) have income that exceeds my minimun income qualification.  But these 3  people have been roommates for 2 years now and are used to having co-signers , so I thought I would add the co-signer for extra security for me.  

Thanks in advance!