They are simply driving the economy.

That's because not only do they have strong returns, they both have growing populations, growing jobs and diverse, modern economies which is critical to the long term value of the asset.

My concern would be the diversity of it's economy and industry and what the economic drivers are.

I think, all modern economies, 'reward' people who invest capital into the market and take risk, as they would be be keeping the economy humming along, something the government on its own cannot do.

We have had 9 years of a booming economy, give or take.

If you wait until the balloon maturity and the economy has taken a downturn you may be faced with a tough task of refinancing your note even though you have made every payments, etc.

I would recommend you should be looking in a growing economy close to a big employer in a big to medium sized city. 

We have now acquired 50 lots in one development and would like to move faster, building 10 - 15 at a time to get better economies of scale.   

I'm currently using moving.com and city data but it's quite an exhaustive process copying down all that data

A lot of investors (including myself prefer multifamily due to the economy of scale.