What freshwater tank-cleaning fish tolerate salt?

I am getting ready to trade in all of my Red-tailed sharks, Gouramis,
Angelfish, Rosy barbs, et cetera, and turn most of my seven tanks over
to housing just Fancy Guppys, Platys and other live- bearing freshwater
fish, fish that I'm told do far better with a wee bit o' salt in their
water. I am also keeping a few of my Plecos, and all of my Corys [my
favourite fish species], and some male and female Bettas. But I have
heard that those species really don't do so well with salt in their
tankwater, so they will go into the tanks that won't be getting any
salt. Could you please tell me what common freshwater fish species
helps to keep their tanks clean, that like a bit o' salt, won't hassle
the other fish, and have as little possibility of eating the fry as
possible, whenever they're born and I'm not there at that moment to
transfer them over to the ten gallon tank that I have had set up for
some time, just for the baby fish? I figure that if I can start my own
little 'fish farm' right here in my home, then just maybe with all of
the extra fish that will be born, I can trade them for fish food, et
cetera, over at my LFS. But I would like to have some kind of
tank-cleaner fish, something very peaceful, like the Cory species, but a
species that can tolerate the salt that those above mentioned fish both
like and need. Thanks for your help,...
Pax Vobiscum,...~Dean.