Which would be a great first investment for a 20 year old in order to start getting some skin in the real estate game, purchasing a duplex or a property in foreclosure at an auction?

Either will work.  What it boils down to is do the numbers work for you and do you have some cash reserves to do any repairs that come up.  Keep in mind at a foreclosure auction you need to pay in cash that day as they don't allow financing for those.  Definitely do some research and find out what houses rent for in the area.  Not all foreclosures are a gem some can be total money pits with significant money involved to get it rent ready.  I have seen it way too many times where someone gets in way over their head once they find out the house had all the copper piping, air conditioner and kitchen appliances, cabinets stolen.    Sometimes it can get messy if someone is living in it.  My uncle had someone that wouldn't leave.  It was a big mess going through the courts and getting them out.  Once they were out they took the liberty of trashing the place.  Over 25k in repairs just to get it rent ready.  The house was still worth it, but not everyone has that kind of money sitting around to do that.

@Devin Howard dude I wish I would have bought more properties in my early 20s. Buy everything! No really....figure out which niche you want to be in and get started.

@Brent Paul thanks.

@Adam Mitchell how would you say I should go about getting the money to start off if I have little to none?

@Devin Howard learn to wholesale if you are starting at zero. The name of the game is finding deals. If you can learn to do that, you will have people asking to invest with you.