Any ideas Choose cities in safe and economically diversified areas with above-average income and population growth.

Just make sure you are as efficient and economical as possible.

I'm a recent college graduate with a degree in math and economics. 

Given the vague post, it's really hard to say.While I do work Riverside County and currently belong to the Estate Planning Counsel, I don't go out of my way to do business in the Palm Springs area because of the high price volatility during low economic times.

Many areas of DC offer amazing appreciation but are in gentrifying areas which can carry economic sensitivity risks.

Yes the San Diego market can be a tough one to get started in, if you decide to invest out of state choose cities in safe and economically diversified areas with above-average income and population growth.

For those of you who care about the broad economic outlook in your investment areas, here's the recent economics report from this month. http://www.jec.senate.gov/public/_cache/files/b2fb1607-cbaa-4d20-871f-c58170cbf5c0/jec-state-economic-snapshots-september-2016.pdfIf that link doesn't go through, google for 'senate state economic snapshot September 2016' and you'll probably find it.

The barrier is not technological capability - there are 10s of thousands such buildings in Europe {search on Passivhaus} - but lack of will (economic and political).Equally important, and potentially more difficult problem to solve, is retrofitting of existing building stock to achieve significant energy use reductions in a cost effective manner.  

Both of these markets seem very attractive and especially resistant to overall economic downturns.

But, typically I've noticed many of the residential buyers base their purchase on their needs and can let their emotions get the best of them.Both require you to act in the best interest of your client, but there is much more black and white on the commercial side where numbers really drive investment sales pricing and can be influenced by micro and macro economic factors.If I were fresh out of college and living at home I'd get started on the commercial sales side.