Any advice on what my mother could do financially with the sale income without buying another property?

They will need to see the last few years tax returns, bank statements for the last 6-12 months, pay statement, and probably have you fill out a personal financial statement showing assets and liabilities.You don't want to wait until you have something under contract to do this.

What would you do with/where would you put the money to work (real estate or not) if you had aspirations of being financially free in 10 years?

Perform your Due Diligence, Review the Financials and Budget, Reserve Study, ByLaws and Rules, Is it Rentable, What are the Board Members like, FHA Financing Available, etc. 

Here's one. http://www.getricheducation.com/project/163-home-e...Basically, done right, instead of parking your money as an equity (paying off your mortgage), use that money to buy more houses, and you'll be financially ahead. 

Hi Liz,I think that this goes back to a basic financial concept of risk and reward. 

(that phrase may already be trademarked but I have no financial interest in capitalizing on it... it's just sound advice!)

So if I understand you correctly, you usually know about what you want to pay prior to seeing detailed financial info right?

TL;DR: Looking for a financial analyst/planner to help me with quantitative tradeoff analysis to help me decide whether I should sell (some subset of) my 5 rental properties so I can afford to purchase a single family home and stop "throwing away" ~4K/month on rent.

I certainly understand your mindset, however I would go with the 2nd rental property rather than paying off the mortgage right away.You might initially have less cash flow, but rental income should increase while your mortgage payment should only be decreasing (assuming you don't have an adjustable rate mortgage).I also like the idea of having more than 1 rental property because, if each property is cash flowing like they should be, you have more of a financial cushion during periods in which one property is vacant.