Help for cancer patient

I am a cancer patient -- I have a rare and aggressive cancer called Leiomyosarcoma -- Stage 3.   My primary oncologist is 200 miles away (400+ mile round trip), and my regular chemo treatments are 25 miles away (50 mile round trip).

My car is 15 years old, and my husband's car is 12 years old.  My car is actually the more reliable of the two, but we are concerned that car troubles might interfere with my treatments by hindering our travel.

We are looking to get a reliable, used vehicle --- 2-4 years old, hopefully.  

Though I am still working, my husband is on social security disability, so our income is limited, and getting a good, used vehicle is beyond our means.   We are hoping for assistance from kind and generous folks.   Any help is greatly appreciated!