What is the relationship between Waitwell and Foible?

Waitwell and Foible seem to love each other, but their relationship also seems to be motivated by greed. They each agree to help Mirabell in his schemes to marry Mrs. Millamant. Waitwell is Mirabell's servant, and he was married Foible as part of his 'reward' for helping his master. Foible may well have considered getting Waitwell as a husband as part of her 'reward'.