Some strategies to lessen the negative cash flow are: house hack and rent out the other unit as a mid-term rental (to traveling professionals or for people temporarily displaced because of insurance reasons like fire) or short-term rental (business or vacation).

Given this is where my major operating expenses fell (beyond taxes and insurance), keeping this cost lower, by average, helps my cash flow.I invest in older neighborhoods, so the 2-4 unit properties, typically have single water meter, maybe single electric, and many have radiator heat with a single boiler.  

Your current home would rent for $1800 and PITI (principal, interest, taxes, and insurance) is $1250.

You will have income (rent), but then you'll have expenses: taxes, insurance, repairs, turnaround cleanup, eviction/attorney costs, vacancy factor etc.

Make sure you're paying attention to taxes and insurance as well!

I have a deal set up with an insurance company that uses this for when they have a flood or fire and they have to put their insured somewhere.. 

I expect it to be moderate size rehab which to me means no significant plumbing or electrical and no walls being added or removed.  

@Dennis GallagherIt's my understanding that the "Income-Expense Ratio" primarily use operating expenses as the expense variable, which includes costs like utilities, property taxes, insurance, maintenance, repairs, property management fees, and trash removal, all of which are considered when calculating a property's operating expense ratio (OER).You calculate OER by dividing the total operating expenses by the gross operating income of a property.

Invest in a security camera—we had a break-in where someone lived in the house for days and stole appliances, which insurance didn’t cover.

The 70% sounds appetizing but 70% of nothing is still nothing, so make sure you clarify all the financials, insurance for damages, etc.