Renting to Young Couple

[Ayodeji Kuponiyi]

Hi fellow BPers!

I'm renting a unit from my duplex and a young couple are very interested. Both are in school with one on a scholarship and are working however...the boyfriend works for his brother's construction business and doesn't have W2 to prove income since he gets paid cash. The girlfriend is a waitress and receives tips. She assures me her father would pay $600 leaving them to pay the remaining balance (I'm asking $950 for rent plus $25/per pet/per month) They have 2 pets so rent comes out to $1K/month. 

I asked if her father would co-sign and she said he wouldn't so I asked for her father to write a letter saying who is his and that he will pay $600 towards the rent for the duration of the lease and to have it notarized to which she assures is understandable and doable.

Should I consider them or keep looking?