courtesy car

I got my PPL about 5 months ago and I’m starting to look at doing trips to locations to spend the day at. I am currently 18. From what I’ve heard before, you can’t rent a car if you aren’t 21. What about courtesy cars?

I was just reading this article in AOPA and it made me think: https://www.aopa.org/news-and-media/all-news/2018/april/24/code-of-the-courtesy-car I have experienced some interesting rides from small airports and I'm sure there are some great examples of courtesy car craziness out there...