Odds of Hanging On
It's difficult to make a career in retail nurseries; it's unlikely you'll hang on throughout your working life if you don't become an owner of a nursery.
That said, if you can scrape by without much in the way of income, and you genuinely enjoy the work, you can hang on for quite a while. Just say goodbye to vacations, fancy clothes, a decent car, and the other amenities you might expect to save toward throughout your working life.