There certainly is a cost to the broker but a local/regional bank typically has a portfolio allocation limit that may limit what they can offer you no matter how good the property is. 

There is an hours requirement but also it states that you MUST spend more time on REI than any other activities(s) A read a tax case not too long ago where a surgeon tried to qualify because he self managed his whole portfolio, yadda yadda...Ultimately the IRS said you're in the Operating room for 10 hours a day 6 days a week.

My goal over time is simply to create a modest portfolio (maybe 5-10 properties) that helps me on my way to financial freedom; I have no aspirations to become a professional landlord or big-time real estate investor. 

It also might be the start of your rental portfolio!

Fill up the first "easy" 10 investment mortgages, and then move to portfolio lenders.

I have been thinking about strategies of growing my real estate unit portfolio in size, but any way I looked, I was running into limitations (high LTV for conventional loans, expensive real estate with low cap, 1031) but nothing felt quite right until I came across the BRRRR strategy.

If building your portfolio or managing what you currently have is a stress after the success you created, I would think this would make it easier to hold on to or acquire more. 

My father has been trying to get me to invest in commercial (his wheelhouse) for the last decade, and after seeing his portfolio grow in that timespan, I'm kicking myself for not starting that journey sooner. 

I would think that you could focus more on REI and not divert a bunch of attention to starting another business and as you invest and grow your portfolio you will learn from those whom you hire to accomplish tasks.

I don't know where the name "flipper" comes from, sounds negative to me, I am an investors that assigns real estate for a profit, have been doing this for over 40 years, have a large portfolio of properties, an auctioneer and developer of commercial properties.There isn't much I don't know about assignments (flipping) - what would you like to know?