Do you know of (or yourself built) a product that solved a niche problem and was not made to earn profits? Later it scaled up and is doing okay to awesome in terms of revenue?
Around 2010 I worked for a project in Jakarta and found out that there was no website for apartment rentals, which was a local gap. With a local co-founder we built Bazarooma [1] (defunct now) which was a full stack platform (consisting of a property portal, backoffice, phone apps, consulting and operations) which allowed organisations to set up and operate their own real estate websites. Indonesia at that time had >200m people with a strong urbanisation trend, so I wouldn't exactly call it a "niche problem".
For a long time it seemed like we wouldn't make any money off the venture (lmk if you're interested in the reasons), but we made a successful exit in the end.<p>[1] <a href="http://blog.bazarooma.com/" rel="nofollow">http://blog.bazarooma.com/</a>