Is exploitation considered forbidden (haram) or disliked (makruh) in Islam, and is it deemed a betrayal if a poor man exploits a rich man by accompanying him then abandoning him?

The Shari'ah evidence indicates the permissibility of one person hiring another, as stated in the story of the man of Midian: (He said, "Indeed, I wish to marry you to one of these two daughters of mine on condition that you hire yourself to me for eight years.") And the Prophet, peace and blessings be upon him, said: "I used to herd them [the sheep] for the people of Mecca for a few Qirat." If the agreed-upon term of hire ends, or if the hire is on a monthly basis with no specific duration set, then there is no blame on the hired person for leaving the employer.