I'd say 4 people with interest would be enough to start the OOC. 6 - 7 people at the most. There will also be NPCs that may or may not join up with you depending on how the party plays.

Last but not least, death will be a real consequence for mistakes in this RP. No one is immortal just because they're a main character and plot armor will be very minimal for everyone involved.

That being said, I'm actually excited to start this thing so let's get some interest going on here!