Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

We work with downpayment assistance lenders that can give you a 0% interest loan to cover your downpayment.

The core-4 consists of a realtor, contractor, property manager, and a lender.

Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

Make sure to connect with local lenders and brokers too.

conventional loan with 20% from private money lender How did you add value to the deal?

Here is a summary of the book.https://www.nateliason.com/notes/long-distance-real-estate-investing-david-greeneThe book also mentions the importance of having a rockstar Realtor, contractor, lender, and property manager.

What are the requirements lenders look for in this scenario?

It's all available public information.He is pushing buying properties for full asking price and using gap lending "gator lenders", (unsophisticator investors), to lend the money for the deal to close. 

Likely a retail mortgage lender with extremely high margins.