Although it may not be feasible for you most people that I know that are aching to get a property will partner with someone that can obtain financing easier.

Many banks, including Wells Fargo and SunTrust, offer an online bill payment service that issues scheduled and recurring payments (either as an ACH transaction or as physical check) to vendors of your choosing.

- ACH option?

Your tenant will have the option to pay by ACH or credit card. 

From the buyers end I've observed (or more accurately been told during my own loan experiences) the decision can take minutes or hours up to a few days depending on whether the underwriter is in house or not (or out of the office or has a tummy ache).

I would like to start with 3/2 SFH OR small MFHs (ideally duplex) while I gain my REI muscles.

And don't be afraid to exercise that "no" muscle. 

Payments are free if the tenant uses ACH, Tenant pays 2.75% fee if they use a credit card.

I like the simplicity of one payment per month done automatically via ACH so nobody has to write a check, drop off cash, or go to the bank.If you do go down that road, how about thinking about charging a bi-weekly rent rate.  

Rentalutions has other electronic options, including the option to pay rent with Bitcoin which clear much faster than an ACH payment.