Some folks in the interwebs asked for a sample of how to spawn things procedurally via blueprint.
Here is a sample project for 4.9.2that illustrates the method. The main idea is to store references to Actor blueprints. In this project I have two base actor types, planets and houses. To begin your dissection, start in WorldBuilder->BeginPlay.
The primary work-horse in the project is the WorldBuilder actor. The way it is meant to work is that you drag a WorldBuilder actor into any level, set all the parameters in his dropdown and when you hit play BOOM it creates everything.
There are lots of ways to go about this and I could list a dozen caveats and issues with this project. It’s not perfect, but is meant as a starting point for those that aren’t sure where to begin.