Also, is it better to go through a broker, who has access to multiple carriers, or directly to the source myself? 

I work for an insurance carrier that specializes in rental properties.

The state has lost almost two dozen insurance carriers so there are not many left to choose from at this time. 

Find an insurance broker in the market of the property, they can shop the carriers that are most competetive and save a lot of time.

I have paid about $6.00 per month per location for the umbrella policy, They said they received an industry-wide as well as nationwide rate increase from their carriers on the umbrella policy and said if I want to keep the umbrella policy, I have to pay more than $100 per property more!  

All flood insurance is backed by the NFIP, the carriers just service the policies.

Most Insurance carriers will insure 1-4 family owner occupied homes under a homeowners policy.

However most major carriers will not insure roofers, so in a case such as that, you must go to outside lines.

I will send you their info.If you go out an buy a single policy for just one of the risks, here are the different policies types and when they need to be used.Vacant Building policy - no renters and NO rehab going onBuilder Risk policy- Vacant and on going rehab Landlord/Rental Property policy - Tenants are occupying the propertyIf you purchase the wrong policy, the insurance carrier could deny claims stating you "misrepresented" the risk.

@Storm Silva Insurance agents are either captive or independent with their affiliation to the insurance carriers.