Tenant Troubles-Will they move!?

[Anna Maher]

We recently closed on a 6-plex and are living in one of the units.  We acquired 5 tenants. I was given 30 day notice by a tenant who is on a month to month lease the other day via text message.  I called the tenant and told them I would need written notice. The tenant has yet to give me written notice and has not paid this months rent.  I told her she would still need to pay for the full month of rent and the tenant told me today that she is not planning on paying until the 18th.  I told her she would be liable for the late charges if she waited until the 18th.  Is this worth even messing with or should I just file eviction and get them out?  In the county I am in (Jackson County, Missouri) an evection takes 45-55 days best case scenario.  Anyone have any helpful insight?