This.

I started a bunch of niche job boards (pythonjobs.com, bigdatajobs.com, railsjobs.com, etc) using a 3rd party platform - but wasn't happy with the platform so built my own.

Fast forward blood, sweat and tears I now offer the platform as a SaaS offering for other looking to create niche job boards (www.JobBoard.io).

Starts out as simple CRUD - gets much more complex - especially when multi-tenancy is involved.