Thats a pretty broad question as it yaries a bit, most Hortics would be self employed as therea re not many employers out there for them.
As a self employed Hort you are maybe doing something like garden design or Maintenance where you are competing against lesser qualified persons.
I would imagine the likes of Teagasc or dept of Environment would pay decent wages or the County councils but I am afraid I dont know them off hand, somebody working in a Co Co might have access to the pay scales or watch for adds on the papers.