The root כרה has several meanings in Biblical Hebrew.  The most common is the dig (a ditch or pit or cistern).

In Hosea 3:2, however, it means to purchase:

 וָאֶכְּרֶהָ לִּי בַּחֲמִשָּׁה עָשָׂר כָּסֶף וְחֹמֶר שְׂעֹרִים וְלֵתֶךְ שְׂעֹרִים:

where Hosea takes (purchases) a wife, and he tells how much he had to pay for her.  The root כרה clearly means purchase in Deuteronomy 2:6.  The Israelites are passing by the land of בני עשו, and they are instructed not to fight with them, and to purchase any food or water that they require:

אֹכֶל תִּשְׁבְּרוּ מֵאִתָּם בַּכֶּסֶף וַאֲכַלְתֶּם וְגַם מַיִם תִּכְרוּ מֵאִתָּם בַּכֶּסֶף וּשְׁתִיתֶם: