Some suggestions....

By the time a person made such a serious commitment, they probably would be established in a given tradition. If for instance you had experience through study and practice of one of the Tibetan traditions, then you could visit a monastery or abbey and ask them about the process. There is an abbey near me, and when people have joined it as novice monks or nuns, it has been after an extended visit of some months. During that time they were able to see what the life of a monk or nun was like and decide if this is something they really wanted to commit to.
In Thailand and a few other countries where Theraveda is the dominant form of Buddhism, it is common (sometimes even culturally mandated) for men to become a monk for a shorter period of time, as little as 2-3 days up to about 3 years, but in the Gelug tradition of TIbetan Buddhism it is meant to be a life-long commitment, though people do on occasion, "break their vows," and return their robes and return to lay-life.