Noone will pay, it'll be free as I'll probably be stealing 3D pokemon models from the internet to stick in there.
Yes there will be nests of pokemon.
There will also be quests and some kind of radiant quest system with the Professor after the main story line is complete.
Also there will be guilds like a Ranger's guild and an explorer's brotherhood, not to mention you could join Team Rocket.
Sure it's a lot of work, but my god wouldn't it be worth it.