Different fields per taxonomy term A classified like site requires very different fields per category or taxonomy term.  For example car will need fields like milage, model etc.. while a house will have no. of bedrooms, sqr. feet etc. I am finding different ways to do this but not sure which is scalable.  I will also be using faceted search api.

First Method:
Create a generic entity with common fields and programmatically create custom entity per category which will be related using entity reference. 

Second Method:
Create single entity or content type with all fields and write logic to hide and show fields per category. 

Third Method
Create content type per category.
If the fields differ markedly, that's a case for a different content type.

e.g "Vehicle" and "House" would be two distinct content types with their own fields - much easier in the long run.