Even a last minute lawyer who may not turn out to be ideal is better than no lawyer. A public defender may also be an option in some cases.
When you say the 'magic' legal words "I want a lawyer", they should not talk to you anymore until you have one. In most cases, you are or will be at home with plenty of time to find a lawyer. In some cases you may find yourself detained/arrested ("Am I being detained? Am I free to go?" are other 'magic' words). They may try to tell you that if you would only talk to them, they would let you go -- they are VERY LIKELY lying.
Do not trust that you can tell or sense if they are lying or not. They are experts at tricking you, they are trained and have lots of practice in it. They are legally allowed to lie. (In my personal experience, they did lie about exactly this -- they said "if you just talk to us, you can be on your way", I talked to them, I got arrested anyway.).
Getting arrested sucks; talking to the police without a lawyer can make it much much worse.
tldr; no, you don't need a lawyer in advance, you can ALWAYS say "I would like to remain silent, I would like a lawyer", and you always have this right, and they can not talk to you (or use anything from talking to you) without a lawyer once you've said this.