If you're slowly increasing but still slightly under market, have a better product, or better service (or all 3) and have rental comps to back it up, if they start to ask you can highlight these points. 

Look at State Employee's Credit Union (North Carolina) and check out their mortgage products.

I'm a product of my environment. ;) 

Definitely a more niche type of product, but, incredibly useful, especially across the Midwest where many rental properties are less than 100k.

And when demand is high, the product goes to the highest bidder.

Of course my buyers are ALL owner occ's so different product and different buyer but probably more demanding than the investment buyer who is buying a basic rental house.

Work with a broker who has access to a large variety is going to help you find an appropriate option for your situation vs a direct lender who can only sell you their limited product set. 

If you have any claims or some list particular claims in that time frame they will not accept new business from you.In speaking with the product managers I've given the example of a client with 50+ locations paying over 45k per year in premium having a claim for $10,000 and would they take the total account into consideration when this client buys another property... the answer was a hard no. 

There is no one best product.  

From a publically available standpoint, Air DnA and Pricelabs puts out great data for their paid products on nightly rate, occupancies, etc.