You are still going to get the best rate possible with your significant down payment and with good credit I'm assuming.   

Quote from @Josh Lansberry: You will hear a lot of people bad-mouth him, but Dave Ramsey can teach you how to get financially savvy real quick.

Quote from @Rafael Valdor: I hear horror stories about renters all the time, but that doesn't mean all renters are bad.

I don’t have much to add for wholesaling other than to remind you to maintain integrity - too many less scrupulous wholesalers have given the name a bad rap.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

Anyone trying to tell you a certain asset class is good or bad these days is probably trying to sell you something.

Used PSI last year, they did a bad job, the snow wasn't even bad last year and with several attempts asking them to do better within the terms of the contract, they still sucked. 

Can easily get fee worksheets and run credit/DU 3.

We both have good credit but my lender made it seem like there was no getting around putting less than 25% down on an investment property.

You have used home equity lines of credit to purchase investment rentals and want to know the best way to pay down the HELOCs.Between the two properties you bought, after expenses, you have $250 a month positive cashflow to use.What I like to do is pay down some principal every month with my positive cashflow.I use my extra active income from real estate commissions helping other investors to pay down the principal even more which just frees up that credit for me to use again.I know I can refinance the HELOC debt before it changes to principal and interest as it is just interest only payments as yours are.One difference is the cashflow, I have greater positive cashflow and could make the principal and interest payment in the future with the extra cashflow I already enjoy.I always get HELOCs on my income properties as well after purchasing them to pull out as much of my downpayment as possible.