Deciding which properties to Rent or sell?

[Ryan Schmit]

First time poster, but have lingered around BP for a while.  I am an established landlord/flipper.  Been doing this for 12 years now.  I have been buying homes to rehab all this while, I sold some along the way, but kept most and built a portfolio of about 20 rental homes.  The cashflow has been great but the day to day maintenance of the business and headaches of dealing with bankers, subcontractors, tenants etc has me wanting to not worry about growth anymore and even has me considering selling some properties, paying off a few others and just scaling back.  Maybe down to 10 properties,  maybe even less.  I'd keep any that were paid off at that point and maybe a few with smaller mortgage balances. Thinking I could reduce my stress level, reduce my workload and enjoy life a bit more while not taking too big of a hit income wise due to the properties being paid off or nearly paid off.  I read most of the replies to an earlier thread about paid off rental houses and can see that this line of thinking is not uncommon of investors in my position.  My question is, how do you decide what properties to keep and which ones to sell.  Is there a magic formula that you use based on cashflow?  or maybe a return/value ratio, etc? 

IF I do downsize, which I believe I will, I want to do it right, as the effects will be real, and going back isn't really an option as there will be taxes to pay, realtor fees etc.  I do think the benefits could outweigh the cons though, if done correctly.  I'd love to hear everyones thoughts and ideas!