and how one makes money with it.. ??? 

One idea is to make your next property your new primary residence that way, you could potentially get a better interest rate and keep your current home as a rental.Also, a big advantage of real estate is its tax efficiency.

There's also a local one in the area I'm going to check into.

I’m completely new to fix and flip but I have been doing some research, I’ve been looking at distressed properties in my area for example one I’m looking at now the listing price is $359k Arv is $550k the contractor fee would be $33k without materials I’ve been looking at fix and flip loans saying they would finance 90% LTC and 100% rehab .

Real estate is one of the best ways to build long term wealth.

You want to find a match for what you really want to do.

I’m looking to purchase a duplex in Charlotte, with one unit being turn-key and the other in need of repairs.

It sounds like you are just getting started on your RE journey so I'll point you in a few directions and give you some ideas and some things to think about.Firstly, I'd recommend reading all the books on RE - preferably the ones written more recently as the market has changed drastically over the past few years.

- How would one run the numbers on a mid term rental when it comes to startup costs, rental rates, and operating costs?

Obviously it also depends on how much time you have to spend and how much you want to be involved in working on the property, but living in one side makes all of this much easier and a good on-ramp into investing!