We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
Restating doesn't cost anything, only coring does, but you don't need to upgrade your territorial cores for janissaries.
They aren't exactly unlimited, but still, it's a pretty strong ability. It's basically 1000 manpower for 10 MP, which is a really good trade off in the early game.