He is super cute but I personally would worry about the size. A friends Chihuahua has the same weight (she rescued him from being kept in a rabbit cage) and I was shocked how tiny and fragile he was compared to Rocky.
Also accidents can happen really quickly. As we were all sitting in the living room, the dogs playing, my friends tiny Chi fell off the sofa and layed on the floor without moving. He had to go to the vets straight away as he had a seizure. That was really scary and I am sure if he was bigger he would have been fine falling off.
Also I know that she always keeps him in a little fabric crate when she is gone as her other 2 Chihuahuas are a lot bigger compared to him and she is scared of accidents to happen (which I can totally understand).
I am not telling you that you shouldn't get him but just trying to show what can happen and how much extra care and attention he will need. If you think you can handle it than you should get him