Hi Bernard.
I ran across this post from a few months ago. What did you decide to do?
There is always a cold, hard math formula that may indicate the right financial approach, but there is so much more to life than following the numbers or tax implications, especially if you are talking about your personal residence.
My first inclination would be to hold a good cashflow property and buy another home for yourself with the low mortgage rates we still have. Fall and winter can be a great time to buy and get a good deal. If you buy another Duplex or a "functional duplex" with a basement you can rent out, you can keep your expenses low and save up for more investing.
That said, If you love where you're living, go buy a rental on the west side with some heloc money on your current place and a new mortgage. West Valley, Taylorsville, Kearns - they all have some great opportunities for good cashflow. You just have to screen your tenant applicants well. I've got several rentals over there now and another under contract.
Above all, have fun out there!