I think being a landlord is pretty much the easiest business ever. As compared to real businesses, who really produce products and really participate in competitive markets.
You can make a lot of money but it isn't easy money. (particularly in the early years, once you have the property paid for it is much easier)
Landlord is not a job, it's a state of ownership. Owning a company is not a job either. Being a CEO is! And you can be both. But simply owning something is not a job.
You can say property management is hard, and maybe it is. That's a separate thing and the VAST majority of landlords actually don't manage their property. So being a landlord is very, very easy.