:-)Currently neck deep in Bigger Pockets resources, real estate books and other resources to better understand the opportunity, marketplace and best practices of the industry.

The training is the best in the industry.  

He has been employed in the same industry for 35 years, has an income of 100k/year for a company he's been working for 10 years, a credit score of 740, and a good debt-to-income ratio.What would you recommend I do?

You can tighten up your major expense by getting exact numbers.2) The second error is buying at retail or at least my interpretation of your example is buying at retail. 

I did get very lucky on the sale however - I had planned to retail the property, but after showing it to another investor/friend he bought it for his rental portfolio.

Can you find them a retail Buyer quicker than a Realtor?

It is a property with some older office buildings in an older metropolitan area that is undergoing some pretty extensive re-development with new retail and new condos/housing.  

@Jason Dillard   I agree with your premise in non appreciating  markets were its a given that appreciation is not going to happen at any appreciable rate .... in those markets your NUTS to buy anything that can't cash flow significantly and or you have bought it under market ( IE retail value) And it really depends on your ability to scale and run an operation.. you need a crap load of doors bringing in 200 a month to make any serious money  like a 100 or more.

New to the industry, want to learn as much as possible. 

I highly doubt a 3 resi unit above a retail store fully rented in Brooklyn has a negative NOI.