If you look on Amazon, Blu is a no name Chinese brand which does a lot of interesting Android stuff and the quality is pretty ok. Swappa.com is a pretty good place for used phones as well.

If the person has wifi, I might preconfigure the phone to use Google Voice by default for calls and text and use the by the minute plan as a fallback.

If you go with TMobile, try to get something that has 1700mhz as well as 1900mhz GSM. WiFi calling may be a nice bonus (but see my Google Voice comment above).