K.G.
I bought a toddler bed when my son was about one year old. (It was a great deal and would only be on sale that day.) My husband decided to use it right away for naps. He was fine. My husband wanted to get him used to it at night, too. So he bought a little toddler bed side rail, and he's been in it since then.
Kids are really adaptable. My son is able to get out of his bed any time he wants, safely, and he can get back in, too. It's really worked well for us.