It seems that the answer is no, but in this case, why would you want to become a monk instead of staying "normal" ?
A lay person can realize Nibbana in a very short period of time(In few years or even in a shorter period of time) If s/he practise mindfulness all day long with effort. Even a very young lay person can realize Nibbana. Realizing Nibbana isn't about being in a particular place but it is the result of the right living. Not all of the people who realize Nibbana becomes a monk because some of the once-returners becomes spiritual teachers or they are in an old age and they are retired from their jobs etc.
In most cases being a monk is absolutely better than being a lay person because human world is crazy and is opposite of spirituality. The human civilization is the manifestation of the narcissistic human world's madness. But a person's decision to become a monk depends on many factors. If a spiritual person has a sangha and in an old age and retired maybe s/he would not want to leave the lay life and become a monk. A person who realized Nibbana and especially an once-returner is in continous bliss and contentment so s/he would not leave his home If the conditions are suitable for him/her.(Solitude or having a sangha etc.)
So a lay person's giving up the spiritual practise is a wrong idea because realizing Nibbana in the lay life is certainly possible.
By a "monk" if you mean wearing a robe or ordained or lives in a temple or in a forest, then No.
By a "monk" if you mean someone who has the Right Livelihood - who does not touch money, who consumes only what is given who has given up all worldly possessions (and happy to die instead of taking something that is not given) - then Yes.
Having seeing the drawbacks of the worldly life, wanting to end this suffering as quickly as possible, people at the time of Buddha, left the worldly possessions and entered into the Order.
Yes, sooner or later. Whether one can, or not, starting at certain point, at least with Awakening, there is no other livelihood aside of that of "being" a monk. If caught in householders livelihood, not a week to last.
Actually one does not even reach the stream, if not leaving stand and home and give up up normal ways of spending ones times. For more, one would need to leave home and stand first, but that will probably not interest many or simply ways cut off by tendency and deeds.
It's simply the cheat of traders who sell caught the possibility of liberation without giving of proper causes first and the business with such runs well, so well that soon for all there will be no more place and way to walk the alternative of going forth. That's the nature of "communism" and "pseudo-liberty", to try to archiv liberty by telling the caught that they are free if they simply accept equality. That is why, if there are monks this days, for the most, they are actually living a householder live and householder giving householders ordination is already to "normal" way. So be quick, if a door visible!
We live like a chicken who doesn't know what's going on. In the morning it takes its baby chicks out to scratch for food. In the evening, it goes back to sleep in the coop. The next morning it goes out to look for food again. Its owner scatters rice for it to eat every day, but it doesn't know why its owner is feeding it. The chicken and its owner are thinking in very different ways.
The owner is thinking, "How much does the chicken weigh?" The chicken, though, is engrossed in the food. When the owner picks it up to heft its weight, it thinks the owner is showing affection.
We too don't know what's going on: where we come from, how many more years we'll live, where we'll go, who will take us there. We don't know this at all.
The King of Death is like the owner of the chicken. We don't know when he'll catch up with us, for we're engrossed — engrossed in sights, sounds, smells, tastes, tactile sensations, and ideas (home and stand). We have no sense that we're growing older. We have no sense of enough.
[Note: Not given for trade, exchange, stacks and to bind on households but for liberation]
"Painful is the life of a house-holder, and free is the life of renunciation (sambadho gharavaso rajapatho, abbhokaso pabbajja)" ~ MN III 33.
In other words, life of a house-holder is like a busy road which the dust of defilements are fermented always. But life of renunciation is like the sky and a monk is like a bird flies in that clear sky. It's easy for a monk to walk in the path than a house-holder.
Simply because of the conditioning .The conditioning in our daily lives is so hard wiring for some people that they need a long time to change that wiring and the best way to do it is to become a monk as monks practice a complete lifestyle that promotes the rising of their awareness and good qualities.I honestly respect more a person who is actively engaged in life and is still able to tackle it consciously but this you can consider as a training ground .