Getting a puppy is a big undertaking and shouldn't be take very lightly at all. The hardest part about picking out a puppy is which one fits your situation the best. Their are several factors to look at.
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First is how much room are you going to have for your new found friend. You don't want to try and raise a large dog in a small apartment as it does the dog no good or it's something your neighbors won't like much either.
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Secondly how much time are you willing to give your new puppy. Some dogs require more care than others. This should also be a consideration when you purchase it. Puppies tend to get bored very quickly and will chew things up. Are you willing to spend the time it takes to train them.
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Third remember having a puppy in many aspects is like having a child. They are dependent on you for many things. Sure dogs are loyal and can't wait to see you, but just like anything they need proper care. After you make all these decisions than and only than can you find the perfect puppy for your situation.