In most states a landlord has to give a written notice to the Tenant OR post such a notice on the property. Once the notice is posted, and the time permitted by law expired, than and only than can the landlord go to the Justice of the Peace.
I reviewed Texas law and it appears a 30 day notice is required unless a lesser time is permitted by the written lease. Please note this is the time period required BEFORE the Landlord goes to the Justice of the Peace (JP, or what ever Texas calls their Justice of the Peace, District Justice, People Court Judge etc)). Some additional time for the Tenants will occur until the JP ruled them to leave but most times they will be out.
PLEASE NOTE AFTER SUBSEQUET REVIEW OF TEXAS LAW, This may be viewed as a Section (e)violation and thus NO Time period is needed, to find out what is the exact Rule in Texas seek out a Texas lawyer.
If you see them tell them to contact their Legal Aid Provider, but south of the Mason Dixon Line The States do NOT Fund Legal Services and therefore Legal Services provider in your area may NOT do evictions (Do to lack of Funds). Tell them to Contact them anyway and see what can be done
PROPERTY CODE
TITLE 8. LANDLORD AND TENANT
CHAPTER 91. PROVISIONS GENERALLY APPLICABLE TO LANDLORDS AND TENANTS
§ 91.001. NOTICE FOR TERMINATING CERTAIN
TENANCIES.
(a) A monthly tenancy or a tenancy from month to month may be terminated by the tenant or the landlord giving notice of termination to the other.
(b) If a notice of termination is given under Subsection (a) and if the rent-paying period is at least one month, the tenancy terminates on whichever of the following days is the later:
(1) the day given in the notice for termination; or
(2) one month after the day on which the notice is given.
(c) If a notice of termination is given under Subsection (a) and if the rent-paying period is less than a month, the tenancy terminates on whichever of the following days is the later:
(1) the day given in the notice for termination; or (2) the day following the expiration of the period beginning on the day on which notice is given and extending for a number of days equal to the number of days in the rent-paying period.
(d) If a tenancy terminates on a day that does not correspond to the beginning or end of a rent-paying period, the tenant is liable for rent only up to the date of termination.
(e) Subsections (a), (b), (c), and (d) do not apply if:
(1) a landlord and a tenant have agreed in an instrument signed by both parties on a different period of notice to terminate the tenancy or that no notice is required; or
(2) there is a breach of contract recognized by law.
Acts 1983, 68th Leg., p. 3625, ch. 576, § 1, eff. Jan. 1, 1984. Amended by Acts 1985, 69th Leg., ch. 200, § 3, eff. Aug. 26, 1985.
http://www.capitol.state.tx.us/statutes/statutes.html