i.e. what don't I know about managing a property management company that should give me pause about this?

Quickbooks allows for you to add multiple debit & credit cards/bank accounts associated with a company.

Have you considered either studying property management or hiring an experienced property management company?

Someone like SunBelt, but there may be dozens like this company who regularly sell such businesses, works with consultants who have buyers looking for these businesses, and have experience with valuations.Does the business own the real estate or do they lease?

Do you need a title company for a deal you've already made on a small 2-4 unit multifamily?

It is extremely common for PM companies to accommodate for external contractors - as mentioned above, it is your property at the end of the day. 

I know my main investor friendly title company says 70% of those deals that get turned in to them don't close.

REPS is tough to qualify for if you have a full time W-2-paying job or company outside of real estate.If you get trapped with PALs, consider utilizing 1231 gain in conjunction with long term rentals.Current year deductions are only great if you can use them now! 

I have seen big companies have no clue that they need MLO and NMLS to originate in certain states. 

It literally seems too good to be true, but a quote I remember seeing was that the credit card companies are willing to lose millions to make billions.