Two tenants one wants to pay a year in full, what do I do?

[Peter Ricca]

Hi BP Landlords!

I own a SFH rental property. Two female friends applied together, a Nursing Student and a Grocery Store Manager. Student has pretty good credit (650), Grocery Gal has no credit history and is building (zero debt, just out of a long term relationship where she did not even have a bank account).

The rent is $1,500 a month, the student wants to pay her half of the year in full once her student grant clears next week just to get it out of the way and not worry about a rental payment.  

The Grocery Store manager will be paying her $750 share monthly from her full time gig (she makes $2,150/mo)

How do I write up this lease so both tenants are on the hook if Grocery Gal stops paying? I was thinking of putting the grant money into an escrow account and drawing from it monthly maybe? 

Part of me wants to ask her to just pay me monthly, but $9,000 up front seems foolish to pass up. I'm slightly stumped here. 

Thoughts?

- Peter