But Fannie and Freddie's first time buyer programs have a much better deal on mortgage insurance. 

Contact your insurance company. 

Looking for advice on landlord insurance - actual cash value vs replacement cost.

Yes you should - always CYA, it's a business deal just like renting the whole house is, with all the inherent insurance risks, etc.  

You also need to get title insurance too. 

Can anyone recommend any good resources or rules of thumbs for coming up with a ballpark estimate for property insurance when doing a quick analysis of a rental property?   

So you are essentially looking at 1500 a unit for a 3bd- 1200 a year for insurance seems low, to be honest- unless you got a quote for this prop 2160 a year seems low for taxes 1200 for lawn/snow a year is high... this winter was bad, and it also depends on if you have a driveway etc or just street parking Closing costs- you can get a good faith estimate from your lender- they may be a bit higher Also, you want to consider if you would be inheriting tenants.. or if they are way below market rent, 

Contact your local welfare office to insure they will cut off her S8 income if she violates her lease.

IDK exactly what your taxes and insurance are, but this looks to me like you need $5500 a month in rent to be break even.

Add up the cost of your mortgage payment, taxes, insurance, vacancy, repairs, cap ex, and management if you will use it.