What is the best way to safely purchase without visiting?

[Serges Lemo]

Hello real estate pros, 

I am a newbie here and need your advice. I have a great deal on a duplex off the market but it's in a different city that I can't visit due to current schedule. Are there recommended ways to perform due diligence on the property and purchase without visiting and still reduce risks? Note the property in question is in San Antonio Texas. 

Your help would be greatly appreciated.