Anyone building niche or affiliate websites as a side project.

Hey everyone! I am the developer of nichewebsitebuilder.com, an All-In-One affiliate marketing and sales solution with services for helping niche website entrepreneurs monetize their content, generate passive income and build profitable affiliate sites. In light of doing so, I was curious to know how some of you build your own niche sites and affiliate sites. What has been your experience building niche site or affiliates and how did you overcome them?