One thing seems certain you would need to make arrangements with the trainer before hand. I think it would be better for trainers to offer package deals so you could buy 1 level, 5, 10 or all levels of his training at once if you have the money and pps but I doubt the devs would agree.
I like that idea.
@ Catlemur - Well, really it's as realistic as training gets these days. When you buy training from the trainer, it takes 0.0001 of a second for the trainer to teach you. Also the fact that some people can learn by themselves IRL (like people have learnt to play musical instruments without any lessons from anyone), whereas in the land of Yliakum that's impossible.
@Earowo - Diagrams shouldn't be too hard to follow.
I think it's realistic enough for a game.
There really should be 3 ways of training, training by your self without any lessons (Hardest way), Training through Correspondence (Medium way), Direct training from trainer (Easiest way).
Mind that, I'm sure Yliakum has some very rural areas, and some farmers (or whatever else) would have to teach their children how to fight through a correspondence system, or a system like what Bilbous said.