I'd make a photocopy of the student's driver's license or passport, and I told them that this is a contract between me and them and if they break the contract, it would be them getting sued, that they were responsible as an adult with no parents involved. 

Make sure to completely vet all showings social media, copy of birth certificate, drivers license, passport, blood sample, medical records, geneology report.Then be sure to record all conversations, make a journal of your thoughts and impressions of every interaction, be sure to have multiple go-pro cameras on your person, like attached to a helmet or body rig.

What is required is a valid passport.  

No SSN, Ghana Passports on file.We will be requiring full background checks and fresh leases for them (and all other tenants) to remain in the units after their current leases expire 12/31.Anyone have experience or recommendations on adequately screening them to ensure we aren't missing anything?

I use "Fidelity Title Passport Pro" but you have to know a Title Agent who is willing to give you access.

A valid passport, and a getaway vehicle.If the appreciation is really ballooning, maybe take your profits while the market is up, load up on liquidity and be ready to scoop up something really good when it goes to hell.Phoenix is a very bi-polar market.