No guilt. Our hunter-gatherer ancestors shared resources and labor and therefore increased their productivity. One was an adept berry-picker, so another woman would watch (and often, cross-nurse) her kids while she brought in more than the two women could have done if they were both chasing after kids. One man might gather firewood for several households, while another, a very skilled hunter, might bring home meat for several. Shared labor. We weren't meant to do it all in a two-adult nuclear household.
What you're doing is just the modern version. You're sharing resources (money... our equivalent of berries, firewood, and meat) in exchange for someone else's assistance.
It just feels weird because we, as a society, are kind of stuck in this "SuperMom and SuperDad should be able to do the work of an entire village, because their home is their castle" mentality. We feel weird accepting help from someone, even when they are justly and fairly compensated.
Anthropological jabber aside... I had a friend who worked as a housekeeper and she said that a decent chunk of here clients were middle-class (not upper-middle-class) SAHMs. She found that SAHMs spent all day PICKING UP and didn't have time to clean. WOHMs didn't have the clutter of an entire day to deal with. Vacuuming is easy when there are no toys on the floor because the kids haven't been home (though as a WOHM, I know that finding the ENERGY to vacuum is totally another matter).
I know that DH (who stays home with DS during the day) and I (home with DS in the evenings) spend most of our time PICKING UP, and very (very, very, very) little time actually cleaning... until the weekend, when one or the other of us just gets completely fed up and cleans and the other keeps DS out of the way and prevents him from creating further mess. During the week, keeping a "zero balance" of clutter is the full-time job, never mind scrubbing toilets.