[Porsche-O-Phile]

Be sure you know what you're getting into. Dogs are great companions but they are very high maintenance and it can get to be a pain in the ass very quickly. One of my close friends is on her third adopted retired greyhound racer (which I think is admirable) but has to revolve her life around the dog. She can't be away from home for more than about 8 hours so the dog can be walked and exercised (contrary to popular belief greyhounds aren't high-strung or have boundless energy, they're pretty docile but still need to be walked like any other dog).

To that point I'd say some breeds are way more energetic than others and need to be not just walked but actively exercised several times a day or they'll go nuts and start tearing your place apart. Puppies are well known for this but some breeds retain this trait well into adulthood (chihuahuas, some black labs, etc.) Also consider liability. Some breeds can end up costing you a fortune in insurance if you can even get coverage at all (pit bulls, mastiffs, dobermans and other "trendy" dogs capable of hurting people badly or known for being somewhat ill-tempered). Some breeds are known for being prone to health issues too (Dalmatians, Great Danes, etc.) Vets can get very, very expensive. Can you really provide good quality care?

Like I said above - know what you're getting into. Yes, dogs are great but the novelty wears off pretty fast when you have to rush home to go walk them outside in 10° (or 100°) weather, when it's snowing or raining, etc. and can't make impromptu or spontaneous plans, etc. It's a responsibility and it's a lot more than a lot of people realize. You can't just keep them shut in all the time - it's not fair to them and they deserve better homes than a lot of people provide once the novelty / "honeymoon period" is gone and it's just another "to do list" item.