i have had danes for several years now, all from rescue. i just recently lost my senior girl, adopted her at age 7 and she made it to 10 before arthritis took over. i have 2 other danes, both adopted at age 4ish.
if i understand correctly, this would be your first dog? if that's the case, i'm not at all sure a great dane is the breed for you. i haven't read all of the replies so forgive me if i'm repeating someone's advice but dane puppies can be EXTREMELY difficult for someone's "first" pup. where a small breed puppy might eat a HOLE in your couch, a dane puppy will eat the WHOLE couch. lacking enough exercise, a dane puppy will be extremely destructive just because of their size. also, when your dane pup reaches the age of about 7 or 8 months, just when you think he is the most perfectly trained dog on the planet, the "teenage" years kick in and he forgets absolutely everything he has EVER been taught and for the next few months, you will be pulling your hair out. remember...things that are cute for a 40# puppy to do will NOT be so amusing when that dog is 150#!
danes can be EXTREMELY expensive. everything (food/toys/vet bills especially) will be a LOT more expensive than with a smaller breed. any puppy/dog is a lifetime commitment. do your research, talk to breeders (GOOD breeders, not just somebody who has a female dane and wants to experience the miracle of birth or someone who thinks they can make lots of $$$ by throwing a couple of intact danes together)...read everything you can and talk to as many GOOD breeders as you can. i can't emphasize this enough. there are SO many "back yard breeders" out there and danes can be subject to a LOT of genetic problems which, if you buy from a not-so-reputable breeder, you WILL experience somewhere along the line. not only health problems but also inherited behavior problems. there are so many danes in rescue because somebody brought home a cute puppy and didn't realize it would GET THAT BIG (not saying that is you, just saying it happens frequently)...if there is a rescue near you, contact them and see what's available, if you have your heart set on a dane. i would strongly advise against getting a dane puppy as your first dog but perhaps an older, adult dog might fit your bill.
do you have room in your place for a ginormous crate? because if you get a dane puppy, you WILL need a crate the size of manhattan!
getting ANY puppy or adopting ANY dog from rescue or a shelter should be something that you think about and re-think about many times before you take the plunge but getting a dane pup or even a rescue dane should be something you think about 10 times longer.