The waiting list, honestly
How the Texas interest list actually works
HHSC explains that demand for community-based services often outweighs available resources, so names may be placed on an interest list until services are available. Applicants are placed on the lists on a first-come, first-served basis, and the people who have been on the lists the longest are enrolled first (HHSC Interest List Reduction). HHSC lists interest lists for CLASS, DBMD, HCS, TxHmL, MDCP, and STAR+PLUS HCBS on that page. YES uses its own inquiry list through local mental health authorities (HHSC YES page).
For MDCP, HHSC's handbook says names are placed on the list according to the date and time of the request, regardless of the program's enrollment status (handbook). In other words, the clock starts when you call, not when you feel ready.
We are not going to guess at a wait time. The HHSC pages we used do not give a single number a family can plan around, and HHSC posts its own interest list data on its Interest List Reduction page. If you want a current picture, ask the person you speak with, and check that page.
Why sign up now, even if you are unsure
Being on a list is not an eligibility decision. For HCS and TxHmL, HHSC determines eligibility only when the person is offered the chance to enroll (handbook). Meanwhile, HHSC says people can receive Medicaid or other community services while they are on the interest list, if they are eligible (HHSC).