@Chris Kay finding a quality, cost-effective contractor is extremely difficult:(There are thousands of contractors that are great talkers, but rarely perform within budget.Standard bait & switch is to lowball a bid, then once they get started all sorts of things "pop up" that somehow their bid didn't cover.

That's all pretty subjective, but hopefully helps a little.

Can try to reposition to Class B, but neighborhood may impede these efforts.Vacancy Est: Historically 10%, but 15-20% should be used to also cover tenant nonpayment, eviction costs & damages.Tenant Pool: majority will have FICO scores of 560-620 (approaching 22% probability of default), many blemishes, but should have no evictions in last 2 years.

I've argued for this and the powers-that-be do have a good argument that they are still active just in other ways, how to cover labor and actions during that, etc..

Real numbers- purchase 907k,rehab , closing costs, soft costs, 840k, all in 1.747 mil, basis for each unit should be roughly 291kappraisal of each unit minimum 400k , so 2.4 mil if for all 6.I might refi only 4 out of 6, that will cover initial loan amount.

You would  then alert your insurance to it and it will go up but you would be covered. 

We like the short-term rental idea because we could stay at the property ourselves when we want - summer break, spring/winter breaks, etc.Our budget will be right around $1M or less ideally, and we would like a short distance to the ocean.How likely is it that we could find a property as described above and have it cover or come close to covering the mortgage? 

FHA allows the construction or renovation of an ADU on the property by refinancing into a 203k loan, but the property must remain your primary residence.This stuff is subject to change, lender specific, and subject to other factors.

I suspect I will throw more money at a problem Airbnb has no interest in covering

The least states:"Tenant shall pay a "late charge" not in excess of five (5%) percent of the amount in arrears for each month the arrears remain unpaid if any Rent is paid more than ten (10) days after the due date thereof, to cover the extra expense involved in handling delinquent payments.