If she is getting males she will want to make sure they are wethers (castrated) or they will STINK when they get older and can get agressive. Wethers make great pets and no Sr. Reeky-Stinky.
Hoof trimming is also needed if hooves do not wear down on their own__some do, some don't. I would...
The seller will only sell them in pairs because goats are a herd animal and need other goats to keep them happy. It is like having only 1 chicken or 1 goose. They will be miserable without company and need their "herd".