BRRR is great in concept, but actually rather difficult in execution.

In the eyes of lenders, cash flow is king and you'll find they are quick to loan you more money if you have a proven concept demonstrated by a portfolio of cash flowing properties.  

I understand the concept but am curious if this is common practice?

The concept of 50/50 partners is an interesting idea, but issues such as: Who provides construction labor and/or management? 

Im firmly with @Jay Hinrichs on the appreciation concept.  

@Brian Hendler, interesting concept which looks useful if it works as advertised.

or a slightly different phrasing of the same concept: the minimum price these sellers will ever accept is the amount outstanding on their mortgage.

I just added a concept called "anchoring" into my negotiations script with great success.

To do that you have to understand the basic concept of depreciation. 

Cookie cutter concept from project to project is probably the most cost effective. if you have success with vendors and factories in reliability then reinventing every project increases the time invested into the project.