Since the HOA covers the exterior I only need to have a walls-in policy.What is a good way to determine the right amount of building coverage?

You get better rates the more you insure with them, offer coverage for multiple LLC’s or business entities and trusts, and even do named storm if you want it.  

closing on a fourplex in Folsom PA at the end of the month. was going to use a property manager but ill be living in one of the units for the first year( FHA loan) and will only be renting out 3 units. while the 3 units will coverage my mortgage payment it wont cover my expenses.

Make sure your insurance coverage covers your total value replacement and not the loan balance. 

Your other option is some of the Alternative Non-QM lending programs that are out there, there are several that take the Rent Debt Coverage Ratio to determine the income or debt ratio instead of the borrowers personal income, most of these only have a 6 month ownership seasoning to use existing value, one company that has this program is Impac Mortgage, they have their credit matrix online to view at "http://impacmortgage.com/media/forms/iQM-Investor-...

Most insurance professionals can provide a good policy for a traditional single family rental, but for any complex or complicated portfolios, you need to be working with someone who has specific expertise for the REI market and client.Cause of loss form: There are three categories of coverage; Basic, Broad and Special.

We own a 30,000 SF flat-roof commercial property in Chicago that gets full sunlight coverage. 

HAVING TROUBLE FINDING A REASONABLE UMBRELLA POLICY AS I OWN 19 RENTALS.GEICO ETC SAID THEY ALLOW ONLY THOSE WITH A FEW RENTALS.

It needs a roof, electrical, and a few other small items and I don't think my traditional agent will bind coverage from what everyone is telling me.

You just have to make sure that your property is rented and meets the 1.2 debt service coverage ratio with the rental income it brings before you apply for the refi.I am assuming you are planning to buy with your own cash or some form of short term private financing.