Is it obligatory to fulfill a vow to give a monthly sum of money after employment, if the entity contacted [me] for training with a small financial stipend and not for employment?

A vow of obedience must be fulfilled when the condition upon which it was made is met, based on Allah's statement: "They fulfill [their] vows and fear a Day whose evil will be widespread" (Quran 76:7), and the Prophet's (peace be upon him) saying: "Whoever vows to obey Allah, let him obey Him." Temporary training work for a fee is not considered a job that necessitates fulfilling the vow.