Yes, there is a lot of competition in this space. I know because I am an advanced user who often has to sift through them to find an answer. I don't know that there is a ton of money here.

That said, I think that the best way to be successful at this is to make a niche site (or sites) that address certain user communities. I work with a lot of physicists who use Excel for general data analysis (yes, I know, R or Matlab are better, nevertheless it does get used), and their questions are completely different from say, accountants. A site like "Excel for [insert profession here]" is likely to be a good way to get attention from that community and differentiate yourself from the general Excel help sites.

Best of luck with your projects