Within a week, more or less. It's strain and plant dependent. Your grow conditions also affect how long. I saw signs after about 4 or 5 days. Good luck.
Well the seeds were just from an average bag of commercial so not anything of any count really. First time grow so I'm just experimenting to be honest. That and the fact that the whole shipping seeds thing kind of scares me lol.
It varies quite considerably - it's very strain dependant. Some plants will show you sex when still in vegetative growth, some you won't know until after 10-14 days of flowering.
If you've not seen anything after 14 days flowering, check your flowering room for light leaks.