Lanefan
Victoria Rules
And it's specifically noted that the intent is that the PCs will tend to accrue more wealth than the training costs will eat up, so they'll still be able to save up for other things.To me this feels like 'video game' mechanics, and it can hurt storytelling options.
You no longer have the freedom to spend that money on story related ideas. No building a castle, freeing slaves by purchasing them and releasing them, buying a skyship, etc... There is a lot that you can do storywise with PC wealth.
I think that might be the point; though I should ask, @Charlaquin , whether you intend to keep 5e's standard rather-fast rate of advancement or slow it down a bit; because the standard 5e advancement rate will likely see them needing to train at low levels just about every time they sneeze.You also have to stop the action and 'return to town' to level up often.
It forces a sometimes-nasty choice on to the players: to carry on untrained or to stop and train and maybe let things develop elsewhere in ways undesired. Or, as DM you just set the pace of the backstory and plot a little slower, e.g. the BBEG is working on a year-long plan that the PCs have to stop rather than a month-long plan.Or, perhaps travel far and wide to find a master to train you. This is not possible if you have a storyline with a time limitation - which either means they skip leveling up, or they can't meet any such deadlines. That either punishes them for following a story or takes the intensity out of many storylines. That isn't generally fun.
Though this does raise question 2 for Charlaquin: what happens to a character if it cannot - or decides not to - train?
I'd assume players are already tracking their characters' finances; all this does is add one line item per level to that tracking.It is also extra accounting. Some of the most common changes we've seen in the game are aimed at reducing the accounting. Milestone experience eliminates individual experince - and it has been widely used. In the 1980s many of us tracked every meal and every lb carried - but in modern D&D it is far more common to abstract it and not sweat the details as it gets in the way of fun.