It sounds like you aren't the type of CPA that needs to acquire your own business-meaning its a completely different ball game when you are solely dependent on yourself to generate leads/business.

There are three groups of costs:Broker fees and commission splitMLS / National Association of Realtor fees - this is the one no one ever thinks about and is generally the highest initial cost (google your local MLS and check out their initial sign on fees and monthly costs or just give them a call)Lead Generation - should you choose to spend money on it2.

(Either 5% conventional or 3.5% FHA.)You can do a live-in house hack if you wanted...either rent-by-the-room for the rooms you're not using or find a nice place with a basement apartment or carriage house so that you maintain some privacy but still have an income suite to generate revenue.

The quick money from Flipping might be nice, but the long term hold on the cash flowing property is what's going to generate wealth. 

UBTI is not generated from passive rental income.The Solo 401(k) grows over time with compounding of the tax-sheltered income, just like it would if it were receiving dividends on a stock investment.When you personally take a distribution in retirement, you will pay tax on the amount of any such distribution.

Younger residents have tended to leave these areas in recent decades, in many cases pursuing better job opportunities elsewhere, leaving older generations to make up a larger share of those who remain.1) What exactly is the author saying about those metros?

@Jared Coffman one thing to consider is do you want to own and build a portfolio of income generating assets?

The live off all the income their business generates.

When grandpa bought the farm he couldn't afford the house and we were able to bring it back into the family 2 generations later.

Also Commercial Lenders where they don't care about you (other than maybe your overall track record and general credit score) and if the property generates enough income on its own to cover the mortgage + reserves.