Having never owned a turbocharged engine before, I don't speak from experience.

However, from everything I've read, watched, and seen, I would skip it.

Ford did not build their Ecoboost line of engines robustly enough to have decent reliability.

This is not a vehicle I would even consider buying, at any price.

EcoBoost with the 10-speed automatic

I would not recommend going that route,

there's a reason why that engine has got the nickname "ecoBOOM".

I'm not all that familiar with this powertrain, but knowing other high-output EcoBoost variants and other overly complex ford transmissions - I would not have high hopes for this one.

Quite honestly? I wouldn't buy any modern Ford product that's out of warranty...

I wouldn't buy it used, nor would I buy a 2018 with that 10-speed automatic. Not only is it joint GM-Ford design, it's known for having problems, and that is the first year they introduced it. It's practically guaranteed to break down before it should. 

If you want a newer Mustang, get the 3.7L V6 that is in the 2015-2017s. It's naturally aspirated and is paired with a 6-speed Austrian ZF transmission. The V6 has similar output to the EcoBoost without the turbo and no direct injection. 

I have a 2013 GT and my Dad has a 2006 V6. From my experience with Mustangs outside, I recommend adhering to the older 3.7. Those Ecos are faster, but they also are faster at wearing down. Nowhere near as reliable as a Honda inline at all. I personally like the 10 speed, but since it is still a new tranny at that time, it will have issues. The 6r80 transmission is way more reliable and will hold up for a long time. God, not to mention that they have plastic oil pans on those newer models, which ultimately made me say nope to a new Ford Product, especially when I experienced that at my work where we have an Ecoboost F150, and had to have the drain plug fixed due to it all being plastic. Nice looking car, but just like Chevy and Dodge, quality has gone down the toilet bowl.