Backstory: Laravel (PHP mvc framework) is becoming popular as rails and express are seemingly stagnating and falling. As newer developers flock to Laravel, there's opportunity to build kick-started/predone websites.
The Idea: Prebuilt websites for developers.
Deep Dive: You would build a few types of websites such as photography posting platform, two-sided sales marketplace and a basic ecommerce shop. You would sell the source code for these websites.
Validation: There was a popular site for rails that did this a while back (the name escapes me, anyone know?).
Monetization: You would charge a fixed fee for each website, you could sell a limited amount and the price could increase the more are sold.