It does depend on what state you live in, so check with your local council. Some states have minimum space requirements that you must fulfill to be allowed a midget, and others require to apply for a license.

Do you have a particular place you will keep it? Do make sure that you have a place for a bed for it, as they can develop bone and joint complaints if forced to sleep on the floor.

I wouldn't recommend raw fish as a diet as it has been noted that some midgets do have allergies to this diet. It's always better not to risk it.

Make sure your new pet gets regular exercise and socialisation. It might be nice to keep two, if you have the space.

Ensure it always has access to fresh water.

The breed is entirely up to you. Each have different traits that endear them to people for different reasons. You have to find the breed that works best for you. Research is key!