we have been sheep farming in the GTA (out towards Guelph) for 30 years.
When we started we had Corriedales. They are a great starter breed. They lamb easily, are good mothers and flock well. We made a bit from the fleece, but that was with targeted marketing and add value (sorting, carding, dyeing.)
Now we raise Rideaus, mainly for sale to commercial operations who want to improve their flock. Our mature ewes raise about 2.3 lambs each lambing. I wouldn't recommend them to someone without animal husbandry experience as keeping large numbers of little lambs alive at birth is a bit of an art. But lots of lambs per ewe works well for our small acreage. We pasture 70-75 ewes on the 10 acres we own. That is a heavy stocking rate so we have to hay feed much of the year. We do hay on another 100+ acres, some for us and some for sale.
Finding an area with a vet who works with large animals and knows something about sheep is a good idea. Most vets close to the GTA are small animal vets and don't have the licensing for large animal medications. Many of the large animal vets in the area just work with horses. As you get a bit further out the large animal vets often know cattle and hogs and nothing about sheep.
You will want to live on the land where you have your sheep. Otherwise coyotes or roving neighbourhood dogs will rob you of both profit and joy in raising sheep. We have discovered that even with guardian animals (donkey, llamas) the only way to keep the flock really safe is to confine them close to the barn every night.
Property costs are going to be an issue if you need to stay near TO and you want to not lose money on your operation. In Stouffville you will be competing with landed gentry for a pretty piece of country acreage. Factor in building fencing and shelter and the cost increases. Getting land with these in place does not add much to the cost, but it will cost you if they are not there already, especially if you have to hire them done.
A useful website with links is the Ontario Sheep Marketing Agency:http://www.ontariosheep.org/
We love to help people who are starting up in the business. PM me if you want to visit our farm.