Hi Noa,
Not sure how to answer your questions as I have not looked at the aquarium trade from an employment point of view.
There are certainly a lot of fish keepers here and many own aquariums. You also see them in malls and other public places so there are people who offer set-up and maintenance services. Not sure how much money is in it though, I imagine you won't get rich The economy isn't all that great here at the moment either (by the way, which contry are you from?) but most who come here say they do so for the lifestyle, not the money. If you are going to be poor you might as well be poor in a pleasant climate (that depends on which part of the country you live in too)
We have extensive mussel and salmon industries here so perhaps he could branch out into other areas of aquaculture if nothing else is available.
Anyone else got anything to add?