Questions on Handling Inherited Tenants

[Joy Shaw]

Hello everyone! I am recently closing on a multiunit. One of the current tenants has not paid rent for 6 months. The previous landlord does not have a written lease, he has just been renewing the lease verbally so technically she does not have a lease now. When I'm taking over the apartments I will have them all sign a new lease. I would just like some suggestions on how I can handle this situation. I think I can either have her sign the lease and hope that she will pay on time with me. I am leaning towards not having her as a tenant though. If I don't want her as a tenant what ways can I handle this without causing too much problem? 

Also another question, the previous landlord did not collect security deposit. How can I go about collecting it without making them upset?

Thank you so much!!