I hate to be the dissenting voice here...but, I will.
So, as far as space goes, I think you're fine. We've had multiple dogs in our 900 sq. foot apartment. They get out lots, go to the beach, go for walks, and we share a decent sized yard with our neighbor. It works.
BUT!
Something that I've learned is that if hubby isn't pleased with the situation...yo u could have 34987134982714 acres and a 90 room house, and it still won't be enough space! That's the part you want to deal with.
This is just my humble opinion, but I've learned that harmony with the hubby trumps my personal desire to have more dogs. And in exchange for not bringing in more dogs against Mark's will, I get a Newf pup in October! He has always maintained that we currently do not have enough space, but that he IS NOT against another dog. I've always fought that and disagreed. But after our last round of (challenging) fosters, I gave in. We're now on the hunt for a house and I've contacted a breeder that I like, and she has a litter due in October. Its a long time to wait, but its worth it, and Mark agrees.