The phrase "personal favor" means doing something for someone as a kind gesture or act of help on a personal level, often without expecting anything in return. Full definition
We'd consider it a huge personal favor; thanks in advance! (yachtclubgames.com)
Menendez is accused of accepting bribes from co-defendant Salomon Melgen, a Florida eye doctor, in exchange for personal favors as part of a corruption scheme, including helping Melgen with a Medicare billing dispute. (freebeacon.com)
Halloran described the money as a loan and personal favor from Stern, which would boost his credit and help refinance his mortgage amid a divorce. (queenscampaigner.com)