Each of my grand kids were already in the toddler bed by this age. Toddlers are considered to be 12 months up to 24 months. Your child will get on the bed, fall asleep, will not be thinking about it being free time. All mine adjusted to it and just went in and fell asleep. There was not getting up and wandering. Well, one was one of those that woke up at least once per night to have a bottle, he still wakes up occasionally wanting something to eat.
Anyway, we put a gate up in his doorway and the baby monitor would let us know right away if he was moving around.
I think starting now is ideal. The child is the perfect age to do this.
You MUST make sure each and every door to the bathrooms are closed tight. If he can open them put some doorknob protectors on them. When my daughter was a newborn I was working at C R Anthony's and this lady came up and told me her 18 month old son had tipped over into the toilet and drowned. She made me promise I would always keep my bathroom doors closed and it was the best advice I ever got.
Come to find out years later when I was working child care we had to start taking child care classes to meet state regulations. One of the things we learned is that toddlers are top heavy with weak necks and upper back strength. If they tip over into a bucket, a toilet, a puddle, they may not be able to lift their head enough to get it out. Please make sure everyone understands this and make it a cardinal rule.