Renting to someone with a co-signer (what questions should I ask)

[Kyrstin Szewczyk]

I have a rental and am currently accepting applications. There are three that want to rent together. 3x the rent is about $7000/month for what combined income they should have. Two together make about $4000 and the third is job searching and her parents are willing to co-sign. 

I will make sure the parents are aware if they co-sign they need to be responsible for the full rent, not just a third, just as each roommate is responsible for the full rent ultimately. Other than that what should I be asking them either of proof of ability to pay and/or verbal questions.

For instance I'm thinking I should ask about their income but how much should I make sure they make or savings on hand? 

Keep in mind I'm in Seattle so I have to consider each application before going onto another (there's is not 100% complete so this gives me a little lee-way right now but not once they complete it).