He's plenty old enough to be out of a crib. Toddlers fit in toddler beds. They get too big for them after they hit about 2 years old.
Get him a twin size bed or bigger when you're ready for him to have his childhood bed.
But, put a baby monitor in his room or in the hallway outside his door. So you can hear when he wakes up. I'd shut his door or put up a gate he can't get over. If you hear his door open then you get up and go put him back in his bed.
Please make sure every bathroom door and door that leads to outside in any way is completely locked away where he can't open them.
Toddlers and preschool age kids are most at risk for drowning in the toilet or turning the water on in the sink or tub and falling over into it and drowning. Their heads are a bit heavy for their necks and if they tip over they can't pull their heads out of the toilet and they drow.
This is not a joke, it happens and it's preventable. Just keep those doors locked even wired with a loud alarm.