Some of it is fun, some serious, some just following our story, etc.

I will recommend building one where there is either a tourist attraction or putting enough amenities/things to do at the campground where people wouldn't have to leave in order to have fun. 

Wholesaling is a fun business.

Learning is actually fun for the first time in my life and I can't get enough of it.

My Wife and I are fun people who are very easy to talk to and eager to get out there to start making new connections. 

I really did enjoy doing Airbnb, I met a lot of fun and interesting people.

I hunt down solutions for fun and there are few that can hide from me.  

Fun fact, they probably profit until X-5.This model is literally used in every industry and works almost every time to have someone buy a product/service and be happy about it. 

I post this publicly - they are welcome to sue me for defamation, the discovery process would be fun.

You can read a lot but the nuts and bolts that will shape your working days come down to state and local statutes, how working with the local government (Housing Authority, building inspectors, etc) is done, and then all of the fun that comes with leasing and managing tenants.