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.")
Sometimes it happens that you need a car immediately. That doesn't mean that you need to buy a car immediately. There are other options.
Imagine if your house burned down. You need housing right away. Are you going to say, "I need to buy a new house today"? Of course not. 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. Instead, you'll find a hotel, maybe move into a short-term apartment, and take the time you need to find a house to buy.
Cars aren't nearly as expensive as houses (usually) but they're still expensive enough that the same ideas apply. You're going to own this thing for years, you can take a some time to get it right when buying it, even if you need something immediately.