Large breed dogs are mean and vicious
Unfortunately, some dogs have been raised and trained specifically for dog fighting and some owners like to make their large dogs look scary, such as clipping their ears or putting heavy chains on them. However, most large breeds (German Shepherds, Doberman Pinschers, Pit bulls, Belgian Malinois, etc) are naturally loving and intelligent animals who, although large in size, only want to be given guidance, structure and affection.
I need a large yard in order to foster or adopt a large breed dog
Yes, all dogs need daily exercise but you don't need to have a large piece of property to keep a large dog well-exercised. A walk, hike, or run in your neighborhood once or twice a day is what a dog needs (and so do we!). The rest of the day, dogs are just happy to be close to their humans. After all, they are pack animals.
It takes a lot of money to feed a large breed dog
Just because a dog is large, doesn't mean you should overfeed them! Obviously it varies from dog to dog, but large dogs should eat about 10 lbs of food per week, which translates into only a one 40-lb bag of dog food per month. Of course, you might also invest in a few Scooby snacks to reward them when they're good boys or girls.