+1 for trying, it's a very educational experience and a nice project to do but you will find the raspberry pi 3 underpowered and not reliable enough to run an ATM platform on. It will be a very frustrating experience updating all those corrupted sd cards due to power failure, rotten upgrades or just wear and tear. If you want to bring steemit to the ATMs, easiest would be to add it to an existing platform like https://github.com/GENERALBYTESCOM/ It will not only yield you a far more reliable (battle tested) crypto-vending solution but it will also allow you to capitalize and expand to over 400 existing (www.generalbytes.com) ATMs already in the field.