Typically, the only DVDs that are region-encoded are
movie and TV DVDs, for the purpose being to prevent the sales
of the DVD of a movie/TV show in another country/region
where the movie/TV show has yet to be released.
This is the “philosophy” behind region-encoding anyway.
Unless the people making the DVDs intentionally put
region-encoding on the DVD, it is region-free by default . . .
Moreover, I’ve sold his inventory before, and know for a
fact that he does not have 6 different copies of each DVD
to account for the different regions.
Side Note: If you have a portable DVD player or laptop, you can always
use that when traveling to avoid running into region-encoding
problems no matter which DVDs you bring.