What are the biggest challenges people have faced with this. Also how do I make sure to get good tenants?

Pace is no different than the leaders of Hamas or the Sinaloa Cartel in that manner.  

Can keep track of different tenants.

Build - rent - refinance -repeat. in columbus ohio you are buying old houses that are 1900 or 1920 or 1940 and you are in a sellers market. on the other hand you can source land which is a buyers market and build single family homes or duplex or triplexes that will return by renting and pulling cash out on a DSCR loan and doing it again. there aren't a lot of strategies that do this. flipping is different. so many risks. but when someone has a well oiled machine it's all good and less risk.

We have a different spreadsheet for each property.   

Today I'd say buy a condo in DC for a discount, tomorrow that advice may be different. 

Would you take a different approach?

I gave him the difference between Cleveland and Columbus 

I would probably start with something different for your first property.  

There is a very big difference in my point of view hearing from someone who knows someone first hand vs. someone who just goes and does some internet research.