There are many reputable dog and cat breeders out there and some, not so much! The reputable breeders will have no problem with a potential adopter doing background checks first. Most good breeders will take the adopted animal back if requested.
BC SPCA – How to find a good breeder.
Tips on adopting a new dog – Tips on adopting a new cat
No Puppy Mills Canada – Each year millions of Canadian companion animals are destroyed due to the greed of commercial puppy mills, the ignorance of back yard breeders and irresponsible pet owners
The Realty of Puppy Mills – The Humane Society
Unfortunately Puppy Mills are universal