Deals are intentionally open-ended in Mistborn: House War. You’re encouraged to come up with inventive and cunning offers, and to play the game on your terms. If you like, this latitude allows for some really off-the wall bribes, like a slice of pizza of help moving house!
Keep things simple at first and stick to the basics, especially if you don’t know the other players very well. When and if you’re ready to expand your negotiations, discuss it with your group before the game and agree on a set of viable offers. Make sure everyone’s OK with them and keep your house rules consistent within each game.