Magic in the 'normal world' is sort of like coincidence increase. It uses ritual processes to increase the likelihood of X happening by itself through ordinary forms.

So the idea of having a wizard hanging out a shingle on the basis of a ritual book and the Ritual Caster feat is not infeasible. You simply have to develop a set of rituals that are low-level enough that local communities will want them, and can afford them.

What becomes the framework or guiding principle of that set of rituals becomes more important, though. Duny/Ged/Sparrowhawk in A Wizard of Earthsea knows names to call hawks to his fist, and gather the goats, and so on. Will these work for the wizard in community? Maybe, maybe not.

Love rituals? More appropriate for the cleric.
Restful dead? again, cleric.
blessing fields? again cleric.
Warding community boundaries? That could work... defensive lines akin to building walls.
Educational illusions? Community entertainment... rituals that create the equivalent of classic movies broadcast onto the side of the village temple. Homer or the game-equivalent in 3-D?
Home economics? wards of preservation on root cellars or cheese caves or wine cellars?