I am looking at different options for insurance coverage for the rental property I am planning to buy.Specifically, my question is in regards to the HOA master policy.

There are a lot of great options out there; aside from providing the basics (ie. listing tool to get the property published to 10+ major sites, scheduling tool to schedule viewings, tenant screening with comprehensive applications which include nationwide criminal background checks + credit checks + eviction history, digital lease creation tool, rent collection tool, and maintenance tracking tool), some services also offer your tenants additional capabilities which makes it an easier sell on your end when getting them to transition over (ie. their ability to report on-time rent payments to the credit bureaus; this can create an added incentive for making sure they pay that rent on time).

It is helpful to have an option that allows you to achieve all of the steps in one place (ie. listing your unit to 10+ listing sites, schedule showings, screen tenants with a fully comprehensive application, keep track of things like rent payments + leases, and offers several other tools as well -- the ability for tenants to build a credit score up to 40+ points for on-time rent payments which can be enticing for them as rent tends to be one of the largest monthly expenses for most Americans).

It is helpful to have an option that allows you to achieve all of the steps in one place (ie. listing your unit to 10+ listing sites, schedule showings, screen tenants with a fully comprehensive application, keep track of things like rent payments + leases, and offers several other tools as well -- the ability for tenants to build a credit score up to 40+ points for on-time rent payments which can be enticing for them as rent tends to be one of the largest monthly expenses for most Americans).

That's in addition to the normal HO coverage. 

It sounds like you could use a comprehensive plan that takes a holistic view of your plans for the next several years and transactions. 

Property is a duplex built in 1985.Limited water damage coverage and liability maxes at 300K are my two chief complaints about the policy I can have through Heritage.

If you are like me, you carry high deductible....which you will pay if they are uninsured, or you have to submit on your policy and let the carrier subrogate back to theirs, if they have any property damage liability coverage to go after. 

The rules have changed a bit since I became familar with them,  but it used to mean one unit per 1600sf of lot space with height and lot coverage / floor area ratio limits.   

It will involve a loan agreement or promissory note that specifies the terms of the loan (amount, duration, interest, renewal, payments, debt coverage, loan to value ratio, etc).