Lived that when I blew my Class B RV's transmission in Crescent City, CA on the 101 (Van life! Van life! #PortlandiaReference). I was going to be stuck there for a month waiting for parts until I galaxy brained my way out of it by getting my car towed to a dealer in Medford, OR and bought an EV there for below cost the same day, the first EV the dealer had ever sold hence the discount.
1. Is available.
2. If the car rental company doesn't pull shenanigans such as cancelling your rental at the last moment due to <reasons>.
3. Is the kind of model you want or need.
4. Has the extras you like/need (adaptive cruise control, etc).
Etc.
In my experience car rentals suck, I wouldn't want to use them except for when I'm flying somewhere.