Flat fee services, multiple layer and level packages (Silver, Gold, Platinum) have accompanied all kinds of other offerings, tenant and eviction insurance, marketing fees, reporting fees, tech fees, and even talk-to-a-real person fees.

A big issue you might run into is that most lenders will require you to qualify carrying two mortgages in your debt-to-income ratio.

Ultimately, the decision to use an agent is up to you but the good ones are worth their weight in gold and can truly be a consultant for you.

What glitters on a spreadsheet isn't necessarily gold in reality.

Long term it would pretty hard to make a descent profit on a rental that was carrying a 9% loan.  

I have a project where the seller is carrying the note on the home with a 20% down payment.

(Long Days on market) and then using secondary financing for closing and carrying costs.

App folio has a dashboard home page that shows cash in/cash out but it does not show the balance you may have carried over from the prior month. 

Although NARPM may not be widely known, it still carries significant weight.

You could also do a subject to with a carry back for the difference.