Tenant moving out, add on roommate is unresponsive

[Sarah D.]

Our tenant informed us he has to move out due to deployment.  He will be moving out at the end of September.  A month into his lease he added a roommate.  This roommate could not have qualified on his own, has not paid the primary tenant any rent in months (per the tenant, we've gotten all the expected rent), and now is not responding to the tenant.  

I'm hoping for the best but planning now for the situation where the tenant moves out but the roommate does not.  My plan at this point:

1. Check in with our tenant every 2 weeks to get updates on his roommate's plans.
2. If the roommate stays and does not pay October rent hand him a 3 day pay or quit ASAP.  Offer $500 for moving expenses if he is out in 3 days, to be paid once he is out.  
3. Get started with the eviction attorney when we hand over the 3 day notice.
4. File for eviction at the end of 3 days.
5. Learn from this- Never allow a roommate to be added that cannot qualify on their own and seems to have demonstrated a pattern of irresponsible financial behavior.

I have a couple of questions:

1. Is there anything different/unique about evicting one roommate after the other moves out?
2. We will be holding the deposit until the unit is vacant.  My understanding is that the deposit covers the unit, and can legally be used to cover unpaid rent and eviction costs.  Can anyone confirm this is correct?

Anything else I should be doing now or be aware of?  This will be our first eviction.  To add to the fun we live on site!  Which will hopefully be motivation to the roommate to move out with the tenant in order to avoid my scornful glances ;)