No hallway is required, however here's the requirements that I know of.Minimum square footage: This can vary from state to state, 70 to 80 square feet is generally the acceptable minimum. 

If he has a $5MM loan in place, what was that used for / is it coming due/ was it short term/ etc.?

You don’t have to pay $20k+ to learn to broker loans. 

Often, lenders will not act until the differential between current interest rates and the interest rate on the subject loan reaches a certain point.  

Instead of a traditional down payment, I would give them some money (maybe just to bring the loan back to even).The upside if taken over the loan at the current balance, with some rehab and hopefully getting the front lot back would be a nice ROI. 

Name detection is via loan signatures.

My borrower is refinancing the loan to hold the property (BRRRR) and I'm wondering if the new lender will have any concerns with this policy. 

Maintenance/cap ex, insurance, if a rental PM, bookkeeping, misc.The fact you have a loan means 1) leverage 2) equity pay down.In addition, there are tax benefits.So I will do some rough underwriting as an OO non-rental at 95% LTV (because FHA has some undesired consequences that make the 1.5% difference in LTV worth avoiding the FHA).equity paydown: 20% (using OP interest rate at 95% LTV and not counting closing costs). 

I believe the investor may need a commercial loan at that point or could do 3 separate loans since they are on different parcels.

With the FHA loan you won't need a huge amount of your savings.