Sex without a condom at first
I have got two friends who do use condoms, but they have told me they have sex without it for a bit, like, the guy puts it in for 5 minutes at first, and then he puts the condom on, so he can cum inside her.
Is that normal? Isn't the point of a condom to prevent illness and babies? And by doing that, you can still be infected by shit or there might be precum? Or am I wrong?