I suspect with “only” $160k of equity, a refinance to extract money will be difficult as there likely it little to extract at 80% LTV.  

B is a new investor and wants a return, but does not want to be overly extractive towards N (i.e. wants to give N a good deal and a path to ownership).

Even if the numbers work out on this purchase (which to me it looks likely you will extract very little of your initial investment out via the refinance), you have to question if there is another property that would work better. 

This hinders any plan to extract value.You also have an issue with your calculated cash flow assuming financed at an investment LTV. 

Most newbies, can only handle one purchase if they do not find a way to extract much of their investment back out. 

But if you end up hating it, you've got the budget available to extract yourself from that situation and hire someone else to do it. 

But if you don't, you've got a built-in budget to extract yourself, so you can hire someone else to do so while you focus on scaling your business.  10% is the industry standard. 

I ran into the same issues recently trying to extract some equity from a rental SFH I've owned for 10 years. 

From these notes, I extracted the following info regarding your question: Classes of Office Buildings: a.

I know I can extract such information from county records.