Next step....ways to invest after selling...

[Pixel Rogue]

This question is a little broader than 'real estate' as the solution yet looks like a good place to ask. 

We are considering converting one of the investment properties into our primary residence.We might do this once every two years to sell and cash out as we start to scale down. We might use one rental as permanent primary home. 

Biggest question ~ lets say we sell the primary home move into an investment and convert the investment to primary residence, what the some good ways to invest the income generated from the sale of the primary home (ideally in tax minimized conditions.). We are not as interested these days in picking up new investment 'properties' per say ~ possibly open to some type of REIT. Simply moving the funds to a savings/money market/mutual fund account that will be taxed annually on earnings is not desired. Same question if we decide to move & convert every 2 years.