King Anti-Nephi Lehi agrees that they will go if the Lord so directs them, but he is still concerned with their possible standing with the Nephites. He, and his people, are so forcefully conscious of the nature of their sin that they are creating a distance between themselves and the Nephites. He suggests that his people will go, but that they will become slaves of the Nephites until such time as the debt to the Nephites is recognized as being paid.
This offer of enslavement tells us a few things that should be noted. The first is that while slavery is expressly not a part of Nephite culture (see Mosiah 2:13), it is nevertheless a prevalent cultural option. Not only does the King of the Anti-Nephi-Lehies suggest becoming a slave, but so does Limhi (Mosiah 7:15). The suggestion of voluntary slavery is made by two different Kings who are in the land of Nephi at the time of their suggestion. While Limhi is of Nephite heritage, he is the second generation of the people of Zeniff to grow up in the land of Nephi.
This strongly suggests that the practice of slavery was common in Lamanite lands, particularly in the land of Nephi. Slavery was a known practice in Mesoamerica. [Sylvanus G. Morley. The Ancient Maya. Stanford University Press, 1956, p. 159, Michael D. Coe. The Maya. Thames and Hudson, 1999, p. 189]