When could baby start sleeping in pack n play?

Okay sooo I have a small bassinet for the first couple of weeks but I also have a pack n play that has a bassinet but I probably won't use that bassinet that much, I'm not sure. I know I'll be getting a mattress to go inside of the pack n play, when did you guys start putting your babies in pack n play and how did they sleep in it? I told dad to just get a crib but he insisted on getting this expensive pack n play so I really wanna be able to use it for awhile and not have to go buy a crib lol