If you can get in and out of projects quicker, that's huge.

It is generally said that things go better when you're pre-qualified for a loan and could make you close quicker. which may help you. 

They are generally quicker than a conventional, conforming lender with closing time but we still don't want to be in there loan too long so refinancing out should still be a choice after closing.If you still want to use conventional money to purchase (meaning Fannie/Freddie money) then you need to keep in mind a few things:Minimum downpayment on a 4-plex is 25% with Fannie/Freddie (20% is possible with a duplex but not 3-4 unit)If you have a business bank account then you are not required to "source" funds. 

If can can take this excess $ every month and save to build a down payment it would get me there much quicker, and i know would result long term in a greater rate of return than the 401k. 

Which one will net you the velocity return of your original investment quicker to put toward future deals while collecting passively.

I lowered my ROI, but I thought it would be good to pay down the mortgage quicker.

yeah, i don't see why you couldn't do it. people use hml for fast closing in competitive markets to flip said properties quicker. if your timeline allows for a longer time-frame, then i don't see why you couldn't do it (as long as you don't try and flip it in 6 months lol)

Seems to be pretty clear based on the numbers you gave though unless you are saying you will pay off the second in a much quicker time frame. 

If you can use the late fee as a tool to get rent quicker then definitely do that otherwise you will need to send a Notice to Quit for those who are past your grace period.

They do offer the ability to close quicker and don't require an appraisal in some cases but honestly that isn't worth the headache for us, my advice is for columbus go the hard money