They need love and care, and owning one should be properly planned and thought through before getting one. With this said and done, let's focus on the additional bonus of the dog ownership. Both you and your dog will benefit from a healthy regimen of brisk morning-walks, jogs or bicycling. If you have sore muscles, like your quads the day after a heavy leg day for example, a few of these walks will do wonders to bring new blood into the muscles, flushing out the old lactic residue and bring in new nutrients for rebuilding the damaged tissue. And the dog stays healthy, happy, and loyal.
Dogs are different.
I mean, all you have to do is look at a Bulldog and a Greyhound to spot the difference. The Marathon runner would make the mistake of his life if he picked the Bulldog, and the couch potato would have a miserable dog if he picked the Greyhound. You should decide just how much time you'll spend exercising your dog every week, and how big the dog can be considering your living area. A Great Dane in a studio-apartment is ridiculous. When you have a rough idea, look up The American Kennel Club or similar, and discuss the matter with them.