The most basic offering for sellers is a flat fee MLS listing.

However, you would sell these loans at closing for a commission or fee.

you may find it beneficial to avoid paying lender fees over and over again, on 3 properties though if you go with a lender that doesn't charge a ton of junk fees then you'd save doing it separately. 

Flat fee brokerages have been around forever, as low as $295.

.- Do you want to manage the new system internally or have an outside vendor manage it for you for a small fee.- Would you be requiring custom changes often to your digital workflow?

And typically long term rentals don't make it easy to include property management fees into the numbers and have them still work well.I would consider looking into STR type areas where you can avoid the risk of property damages (str and pm insurance covers almost everything that they might damage) and evictions/collections.   

No matter how much planning and due diligence we do, there’s always an element of uncertainty, whether it’s hidden issues like wiring or unexpected price jumps.

And what is the usual fee range? 

Like what Joshua said, purchase price, closing cost, and agent fees are capitalized.

And I believe BP Pro's get a discount on Stacksource's fee.