I run into a store and buy a sandwich and drink)? 

They have helped my parents retire comfortably, paid my kids way through college and been a great way to store and build wealth.

@Lucas MoralesIf you have coin op laundry in the building as well make sure you have a machine that gives quarters as I have had people use the vending machine to get their quarters for laundry and you have to constantly restock it.Personally I would say it’s not worth it unless you are far from grocery / convenience store.

Even just a box store H&R Block type of professional if you don’t already use one to help maximize your deductions and write-offs from the real estate.

If you are up in the mountains, somewhere to store snowboards.

You could be buying a small manufacturer, or a retail store.  

I can even do it with grocery store carts.  

Gas + convenience store, where the gas sales are mainly a tool to draw customers into the C-store. 

Yes, you're missing the underlying appreciation of the house, the value of storing money in a physical asset versus an alternative and capex costs.

It is hard to justify an expense that would eat up all of a majority of your cash-flow.An investor doesn't necessarily need 'any' professional but it really depends on your knowledge/amount of time you have.For example, technically, most people may not need a painter as the tools are available to them in Home Depot or most stores.