No, it won't have negative effects and infact a familiar can have many benifits. Most likly they will have better protection, better health, be happier and have a longer life span due to the magical residue from yourself.
And you can do rituals to allow your dog to become a familiar but truely it is their choice. If you have to force an animal into being a familiar then it just won't work out.
if your dog were your familiar it's fine. but i don't think you can make it one. i think i had a familiar once a long time ago, it's a very deep and special bond. it's more than a love for that animal, you seem to have a connection, you know when the other's in trouble, or where they are at all times. if memory serves, i've seen spells on here, but i wouldn't do them. i don't know if they work, but i don't think you can force a deep bond like a familiar.