Table of Contents
Pokémon training in Sehto is… atypical, compared to the games. Most people keep pokémon as pets and as aids for work they themselves cannot do. Battling is frowned upon, but tolerated - it's hard to completely ignore the Kanto and Johto cultures, after all, even with plenty physical distance to go with it.
Another very important aspect to pokémon - and a reason why many, many people have them - is that they're a cross between 'protectors' and 'weapons', seen as vital for self-defence (especially from other people that have pokémon ^_~).
About 25% of all people in Sehto have at least one pokémon (which then in turn usually provides protection for more than one person). Of those, two thirds have at least two. Having more than five pokémon is considered unusual. Having more than ten is terribly suspicious unless you're a farmer or a pokémon breeder.
The term 'pokémon trainer' does not imply that someone battles. Pokémon trainers are simply humans who dedicate a significant portion of their time toward teaching pokémon in some fashion, be that as helpers for the disabled, as workers for certain chores, as suitable for a life as pets, as entertainment providers (e.g. by performing tricks) or as creatures for battle. Even the very last point is not looked down upon - even if instinct suffices in a pinch, a basic battle training is considered a good thing for pokémon to get if you can afford a basic course (where PokéGyms don't cover it; see 'PokéGyms') or know to teach them the basics yourself. It's when you teach pokémon to battle with the intent of actually doing so on a frequent basis that people start to be wary of you.
PokéCenters
PokéCenters in Sehto are not commonly free. A notable exception is the Togi PokéCenter, which is de-facto communally run (strangers are of course welcome to leave tips); and pokétrainers on the gym circuit may occasionally be granted 'gym leader discounts' when the gym leader announces them and asks for their pokémon to be healed. (That's intended as a favour to the gym leaders, however - very much not the pokémon trainers.)
Prices vary depending on staffing and frequency of their use - understaffed PokéCenters tend to be a little more expensive in an effort to keep their workload manageable and the queues shorter (most notably in Nightclaw) - but shouldn't eat into anyone's reserves too much. Because of the technology used to heal pokémon, prices tend to be batch-prices - the amount of pokémon to heal are divided into batches of six and you pay per batch. As such, getting one pokémon healed costs the same as getting six of them healed.
PokéMarts
PokéMarts are slightly more frequent than PokéCenters, owing to the lack of widespread battling, and tend to sell various pokémon care items (food, chewtoys, brushes…) on top of what you're used to from games - usually predominantly, even. Medicine such as potions, revives or status heals are also sold here, but can typically also be acquired in PokéCenters (that put these items to use, themselves, if there's a power cut, equipment malfunctions, or no pokéball is available for the injured pokémon), and so it's quite possible that a PokéMart hasn't bothered restocking one of those (rarely sold) items when they're out.
Bigger PokéMarts come with educated staff that will happily tell you all about which pokéball to use for which occasion if you have a question. Somewhat unsurprisingly, PokéMarts are one place where battle-prone pokémon trainers are always welcome - owing to the obscene amount of pokémon they tend to have and the amount of money they tend to invest in them.
PokéGyms
PokéGyms are, most simply put, training grounds for pokémon. They're open to the general populace in that regard.
Gym leaders provide several services to people who come to their gyms. The first is pokémon training. The second is leadership for settlement defence, ranging from police-like services to military-like services (though in the history of Sehto, this has been unnecessary, and it's highly questionable whether any PokéGym in Sehto would be competent in fielding this if it suddenly became necessary; but in theory it's part of the deal). The third is fulfilling a 'village elder' function, mediating civil or criminal disputes between people.
In effect, they wield an incredible amount of power within their respective towns - and it's for this reason that they pointedly are not in a position to collect resources from others. Everything given to gym leaders is voluntarily donated - with the note that it's considered socially unacceptable for people to use the gym services and never donate anything, and if such a practise becomes known, people can easily find themselves ostracised (by the city/town, not by the gym leader); so, in a way, it's best to consider PokéGyms 'pay what you like' endeavours. Good gym leaders, like Yarver Bakema, tend to end up rather wealthy for this reason. Since they're very much unable to be a power monopoly (by very design), however, people aren't often concerned about that effect.
In larger settlements (Nightclaw, Vale and Njoty, specifically), the PokéGym's pokémon training service is for advanced training only (thanks to the large volume of people it'd otherwise need to be there for).