I think I have a grasp on the recurring costs such as the mortgage, insurance, taxes, water/sewer/trash, ongoing maintenance coat, etc.

It's going to be a lot of effort on your part to rehab the property, only to pay all of the fees associated with selling a property and make too small of a profit.You should also have a much better grasp on what your rehab costs will be.

If you grasp all of the concepts in Jay's book then you might move on to more 'meaty' type of books.

with about seven employees but he doesn't seem to have a good grasp of accounting requirements for keeping track of all expenses, income etc to be able to do a P&L mid-year if the bank wants that.

Just trying to get a grasp, because I believe I calculated $300 for cap ex when I revised my numbers for this property.

Seems like you have a great grasp of what you are wanting to accomplish it and how you can accomplish it.

Without a solid grasp on what expenses and other costs for each property, how do you come up with ballpark measure of past sales to understand neighborhood opportunities better?

BRRRR goes slightly more in depth and might be hard to understand if you don't have a decent grasp of the basics.Right now, because of the vehicle I'm choosing (Buy and Hold MFHs), I'm reading:Building wealth one house at a time and What every real estate investor needs to know about cash flow.Hope that helps! 

I am also trying to get a grasp on direct mail marketing as a deal generator. 

He seems to have a good grasp on the multifamily market, especially in that area.