'Not in your favor' is the correct expression. The idiom is 'in (someone's) favor' -positive 'not in (someone's) favor' - negative Example of usage: re taxation: "The IRS likes to make that argument...
Favors to friends should have no strings attached and one of the two friends may need a favor or some help more than the other and if the two friends are very close then no one should be counting the...