There is up front costs like dividing the living room into 2 more bedrooms etc plus the simplier furnishing.   

Mathematically, you take the expected interest rate and divide it by 72 to get the number of years for your investment to double.

My dad retained a life estate share of the property with both sons having equally divided remaindership.  

(not the $470k from the past...what you expect on an annual basis going forward)The sum of those three annual items is the numerator in ROE (the "Return" portion).Divide that by your Equity which = $469 ($850 property value - $381k current debt)

When you sell, how is the money divided up? 

Divide this number by .75 or .70 to reflect a down payment of 25% or 30% respectively, and compare that result to the asking price.All the above takes about 10 or 15 minutes max - even using just a calculator.

If you're just looking to lower your payment, then take the total costs its going to take to refinance (at the very least 5k) and then divide that by the monthly cash flow improvement you'll have by getting lower rates.

That is divided 10 ways since you are all equally invested, so 9,100 each.   

Another option is to buy a house, divide it into separate units, and keep one for yourself while renting out the others for more privacy.

Keep it in my name and divide the electrical cost by three each month and have them pay me?