like others have said "money" niches are usually highly competitive and really hard if your just starting out, but some "money" niches are: porn, pharmacy, insurance, real estate, mesothelioma, and alot more... i actually just wrote a blog post about this that you can check out here: Deciding Which Affiliate Market to Promote i'll be blogging about "money" niches soon.
I guess it's home business (internet mainly), which roughly translate, is money. Who doesn't love money?