None. lol.
By the time you setup the tank, and get everything for that, buy shrimp, possibly kill them, buy more shrimp, factor in water, hydro, food, time you spend on maintenance, it's not really profitable. The more tanks you try and get going to get shrimp breeding to make more "profit", is the more tanks, water, food, hydro, supplements, you need. lol.
Have I sold over $1000 worth of shrimp from ones I've bred? Yes.
Did I spend that much total on shrimp and supplies? Maybe. I got lots of tanks for free, built my own stands, light fixtures, etc.
Including monthly hydro and water and getting RO, now have I spent over a $1000 in the last 1.5 years I've been in this including tanks and shrimp? For sure.
Does that $1000 cover the hundreds and hundreds and hundreds of hours I have spent on forums, reading, researching. Nope.
Does that $1000 cover all the time I spend each week on the tanks, building stuff, the space I loose in my apartment. Nope.
Do I still do it. Yup, because I like to, not to make money at it. You need a well setup, fully automated tank rack, a good investment of initial shrimp stock, wait 6month to year to get your population going from that stock, etc to get to a point that they are breeding good for profit.
This doesn't factor in not being able to sell them locally, because others are cheaper or the market isn't there, which means you have to resort to shipping. This opens up, time and money to package and go ship shipments, cover DOA losses, learn how to ship shrimp, loose money from paypal transactions that they charge you for each one.
All of that is based off hoping you don't get a simple bacteria infection if your tank, a bad plant, etc that wipes out a tank of hundreds of shrimp in a week.
I guess to answer your original questions, right now breeding high end taiwan bees like pinto bee's and other true breeding patterns, you can get a few hundred bucks a piece or starting your own pure line of crystals, that in 10-15 years when you have an established name for yourself as a breed, you can get $500 a piece for high end pure red line shrimp.
Otherwise, setup a tank with a neo species like snowball, yellow orange or fire reds and see if you can keep them alive first off. Then if you get them breeding, see if you can find a buyer and work up from there.
I just priced out a "if I had some extra money" what would I build kind of setup to breed shrimp as a side business, not to get rich by supplement my other businesses. To get 12 20 gal tanks fully setup, sump filtration, lights, substrate, etc and to stock the 12 tanks with a variety of 12 species I would want to keep and breed with 40 shrimp of each species, I am at about $7000. To get the rack build, tanks setup, plumbing done, tanks cycled for a good few, get juvenile sized shrimp in, get them settled in to the tanks, get them to breeding age, get them breeding and hope they like the water, nothing happens that kills, them, and get maybe 2 batches out of them that are of size to sell, I am probably a year out from the date I start. So that's $7000 in, plus hydro, water, time, etc for a year before I have some shrimp ready to sell and that provides nothing goes wrong.