Which dog would be best for us?

OK, well, my Mom and I live in Saint Paul, Minnesota, a fairly small house, without a fence, and neighbors upstairs which have a Pomeranian, she's really nice and all, and we can't get one right now, but we are thinking about it, (my job is to do research), at first I wanted a Bull Mastiff, but those are too big for our house, and now I want a Miniature Pinscher, but I heard those need places to run around in, and I want a dog like those, Not a Chihuahua, or anything like that, but it can't be too big, and I still really want the "Min Pin", aka, "King Of Toys" and my mom wants something that could Guard her at night while she's walking it, By The Way, I'm 15. And yes, I know the min is not related to the Doberman, Don;t need to tell me, I just need you're experiences and in-put on what we should get, and I'm going to try and find a Human Society or Rescue Agency, and things, to get the Puppy. Thanks.