"How many disciples can a monk have?"
I guess it all depends. If the disciples are all like me, then a monk would want only one, if that. I mean, how much pain and displeasure do you really want to put these guys through?
In reality, a monk can have as many disciples as he chooses. Martial monks can have disciples, Buddhist monks can have disciples. Some have a few, some have many, some make their entire school base, "disciples". Now, you thought the "real versus fake" monk issue was bad, let's go to the "different varieties of disciples" disciple issue. Some schools in the Shaolin village will take students in, immediately give them a disciple name, and tell them that they are disciples of the head master. They even get little books, given out by the school. I call them, well, "school books". Do I see any evidence of a long standing mutual trust and dedicated relationship between master and disciple when every student who walks through the door automatically gets a "school book", a disciple name, and becomes a disciple? Not really. But, it sure is an easy way for a monk master to rapidly build up a "disciple base", if that was what he wanted to do. It also tends to instill a bit of confidence and moral in the new students, and, if you saw the average living conditions here at Shaolin, god knows they need it. So, again, as in everything else in life, there are varying degrees of, well, everything.
Other monks rarely take disciples, some, not at all. Some monks work under the old system, of "prove your worth to me and I'll think about it". Overall, it seems that becoming a disciple of a headmaster at a school, and a disciple of that school, is an easier process than becoming a disciple of a monk and the Shaolin temple. But, as with everything in life, it's variable.
But, one thing that I've noticed, is that these monk masters all have a similar "feeling" about the terminal future of traditional gong fu (more on that later), and all are aware of the general education in the village which tends to lean towards modern wu shu training. Yes, traditional gong fu is still being taught; some of it is being taught to the students, though much of what they learn revolves around the modern acrobatic competition oriented wu shu. A fear of a loss of the traditional gong fu is heavy in a lot of these monk master's minds.
What I've found interesting, is that each of these masters, has individually and basically decided that they want to pass down all of their traditional gong fu knowledge, as they've learned it, to one individual and very special disciple. In thinking about modern evolution, this is not exactly a safe way to have the gong fu "species" evolve and survive, but, it seems to be the method of choice. Each master chooses one very special disciple, and then, over time, teaches that individual all of the modern wu shu and older traditional forms, with the end result hopefully being, that disciple would "carry on the tradition". Not exactly a safe way of protecting the knowledge, but, this seems to be the way most of the monks prefer to do things.
Who am I to argue with them. So much for all of those theories on evolution.