I think some expenses might be missing: rental license, rental inspection, trash, landlord paid utilities (some municipalities won't allow certain utilities to be in name of a tenant), vacancy factor, reserves for capital expenditures. 

Flip option:If I sell for $150,000-$9,000 (6% commission)-$4,500 (estimated 3% closing costs)-$5,000 repairs$131,500                                   Holding costs                                       5% interest on $126,000 = $6,300 /yr = $525/mo                                       Property Tax 2100/12=$175/mo                                       HOA 360/12=$30/mo                                        Insurance $1,000 estimated/12 = $83/mo                                         Utilities $200/mo                                         Total $1013/mo-$4052 (4 months of holding costs)$127,448 Net sales proceedsIf paid what is owed on Mortgage ($126,000) then not really any profit for me, and no margin of safety.On the above numbers I don’t see positive cash flow on a buy and hold strategy after considering insurance, property management, vacancy, capital expenditures and repairs.

You can take on partners, such as private lenders, equity partners, etc.Other expenditures are just that: expenses with zero return other than continuing on-going operations.Just wanted to put that out there.

What if the inspection comes back that the whole house has cooties or that it's built on an old Indian burial ground or that it's haunted...?

Improving it further with cashflow won't be easy on a multi of that size as your cashflow won't be much per month... and that's assuming you don't have an unexpected big expenditure in year 1 or 2.... which can wipe out all of your projected cashflow early on.

Multi family homes require exponentially more capital expenditures than single family homes. 

@Tom CooperFor larger capital expenditures, you try to forecast when they need to be done.  

In addition, repairs and capital expenditures will be subject to the final tangible property regulations which I briefly mentioned above.You will also depreciate the rented part of your property, which is why accurately reporting basis is critical.

The capital expenditures are expensed on an ongoing basis, as compared to all at once when the money is deployed for a big ticket item.

You'll want to make sure not only mortgage payment is covered but other expenses too such as utilities, taxes, insurance, Mgmt fees, repairs, cap expenditures and vacancy.