Where can I get low cost or free updates to both my medical and financial power of attorneys and my will in Travis County?

Jean, so your in Austin area? If so, Texas RioGrande Legal Aid has pro bono clinics. Google TRLA for info.
Sometimes law schools have probono clinics; UT probono I think only does expungement, but St Mary’s in San Antonio has general pro bono clinic.

Contact the Area Agency on Aging. They are a great resource with many programs that you may be able to use.