The easiest way to have a quick turnaround is to find a wholetail deal....a deal that you get off the market and then put back on the MLS to sell at market rate....maybe all you did was clean up and paint.Here in Chicago, all deals are hard to come by right now...what city are you in?

Integrity goes a long way.You can also give a very generous closing gift, offer additional information/services post-closing, and/or offer a rebate for a portion of your commission at/near closing time. 

@Susan Thelen it’s likely easiest you do this in excel so you can easily modify variables and test the NPV sensitivity.

The paperwork sort of selling yourself is the VERY EASIEST part.

The easiest way to start out is to "house hack" or in other words by a multifamily between 2-4 units, live in one unit and rent the other units out. 

And does your calculation take into consideration the fact that an entire town can burn down, and the only assistance the government will give you is a $700 gift card? 

@Kenneth Lewis if you're 21 and you want a rental property by 24, I think the best/easiest path is to work on a career related to real estate.

The easiest way to view it with Househacking is; the more uncomfortable you are willing to be, the more you can potentially cashflow RIGHT NOW.  

Would there be gift taxes involved as well? 

You say you're open to house hacking that's great, and may be the easiest and the lowest barrier of entry just this has detrimental impact to family formation if that's what you're aiming to do.