> You're always going to pay a premium for getting something fast. For an expensive item like a car, that premium is going to be huge.
At least right now in the US, there is no premium for buying a new car in a single day.
> It's a huge purchase that requires a great deal of research and thought. In the unlikely event that you can find something you can move into immediately, you'll have extremely restricted choices and probably pay way more than you needed to.
A car isn't anything like a house. Pretty much every house is different. The location of the house matters and can't be changed. House build quality varies tremendously, requiring in-depth inspections. There's a ton of paperwork to get through, with 24 hour periods on offers and counteroffers common.
Cars come off an assembly line. Every 2015 Honda Civic is like every other 2015 Honda Civic with some minor differences in trim that you can evaluate online or within five minutes of getting into the car at the dealership.
As long as you know what kind of car you want, which you probably already do, there's nothing to "get right". (Although there's things you could do wrong, I suppose: don't walk in and tell the salesman "hey I really need a car asap.")