The owner gave them notice, and a 'deal'.  2 month notice essentially. 

You are essentially getting the money (cash out refi) at the cheapest terms compared to hard money, HELOC, private lender, etc. 

Essentially the plan is Buy, Renovate, Rent, Refiance, and Repeat. 

I agree in principle but not in practice.

Think of th essential services that people still go to stores for. 

His statements on diversification in this manner was essentially a response to questions about comparing him to stock pickers from managed mutual funds (where they owned 100 or 200 or more stocks and he often owned huge amounts of under 10 - he also bought out companies completely so really he has over 10 but...).Warren Buffett also believes just buying very diversified stock market funds (unmanaged with low costs) is a very good strategy for nearly everyone (excepting himself and a few others). 

A clean title is essential in moving forward on a deal; any unexpected liens can bring the process to a standstill.While this is by no means an exhaustive list of the people you should have on your team, it is certainly a great place to start.

I've seen a few occasions where there was an agreement in principle, but once the buyer rehabbed the property, the seller reneged.

Typically Core assets are used for solid relatively risk free capital growth, value add and opportunistic assets essentially utilize stabilization strategies to generate optimal terminal value at disposition.At the end of the day its all about risk/reward.

While long-term appreciation and tax advantages can justify holding such a property, weighing these factors carefully and aligning your decision with your specific investment strategy and goals is essential.