Even though a Jedi could chose not to take on an apprentice, it was nevertheless considered part of a Jedi's responsibility to train the next generation of the Order.
Only when he turned no one was there.
It was a maze of building, some with several stories others with one.
Of course, there are those who intentionally embrace this darkness, yet Yoda has a response for that as well, emphasizing how this road will only lead to pain and loss.
Once the padawan of Grand Master Yoda, Dooku would take on a young Qui-Gon Jinn as his own padawan.
He almost defeated in a lightsaber duel, severing several of his mechanical limbs before Grievous managed to escape to a control room.