It's lower income and some of our tenants are on voucher programs.  

However tenants who have housing vouchers/grants guarantees landlords the opportunity to receive rent on time.  

You can ask for the HAP contract and most recent lease amendment, both of which are documents the Housing Authority should have.The other issue is practicality - if your area is like most across the country, there is a huge shortage of housing where the landlord will take the voucher so what this means is that it is often difficult for the tenant to find a new place quickly. 

All units have been rented to low-income tenants receiving assistance through voucher programs, and I plan to stick with low-income tenants to help alleviate the low-income housing stock in Phoenix.

They do this in order to protect the government money and not pay more (voucher program) in one area than what tradition rent price/ salaries have demanded. 

You have accepted their Voucher and completed the required form to move forward with the transaction.

If you want to take rent vouchers/ welfare, that is a market niche.

How do you determine rent for the unit and what is the voucher willing to pay?

I'd emphasize that it's not safe for her to live there in the current condition, the city is going to start charging for violations and you can't allow it to continue.In your shoes, I would loop in the Housing Authority caseworker because if she gets kicked out and/or doesn't pay her rent, she can lose her voucher, which would further add to her issues.I have generally found that empathy goes a long long way.

Her voucher is still frozen (at least it better be as she owes me money and The Housing Authority is aware of this).So to say Section 8 is guaranteed money and Section 8 tenants are afraid of losing their vouchers may be true in a lot of cases, but certainly not all.Though my biggest annoyance was with the Section 8 Housing Authority; they were inept.