I believe alot of it has to do with intent, which of course is a very subjective/grey area. I believe if you are not building with the intent to sell, you are in the clear. However, your description of the scenerio does seem to show you are building with at least some intent to sell - I would recommend against doing what you are proposing.
Not to mention, home builds really don't tend to sell for all that much more than the cost of the components, especially online. To many unknown factors and potential problems to make it attractive to a buyer. So... not only are you toeing the legal line, but you probably aren't going to do much better than break even.
If you are looking for ways to make some extra $$$ to fund fund future kit purchases, you may just want to buy whatever the cheap "kit of the day" is today, wait until supplies dry up and sell for a bit more on the secondard market, then buy the next "kit of the day". However, this is an iffy proposition as well, because you never know what is going to come in next - could simply be more of what you already have, at a cheaper price.
Rocko