At this point, this is a retirement diversification move for us to try and have some extra passive income when we retire in 13-15 yrs.I guess the big magic crystal ball question I have is, how can I best assure (in an unsure market and world) that my offers aren't too high and I'm not overpaying for my local market, and won't wind up upsidedown in value? 

It offers a stream of income and diversification to your real estate portfolio.  

Some good metrics to consider can be; population growth, income growth, rent growth, job growth and job diversification. 

While the downside to that is you lose diversification for now, the upside is you have much better economies of scale, easier 1031 completion, and as others pointed out, less competition for that product.

They tend to offer greater diversification and lower down-side risk if you're with an experienced group.

All are passive investments and you get diversification.

That's some nice diversification!

-Passivity and long term growth was important to me as well as diversification.

-Yes a diversification exchange is selling one and purchasing several. 

There are advantages and disadvantages in your plan of diversification of markets.