Think what terriers were initially bred for. Most were put down holes after badgers, rabbits, rats, stoats …… so the chase instinct is high as is the nipping tendency. My JR would run off with an ear cocked my way, like 'I'll be back in my own time'
……… she would also fight with anything larger than herself. Fox terriers kind of bounce along on their toes somehow. Have a word with the owner downstairs to see what her dog is like with others, go for a walk with them to see how it reacts! How often do you meet on the stairs?
However, Norfolk (ears down), Norwich (ears up like the Cathedral
) terriers are 'flat sized'. A dog is to an extent is what the owner makes it, you are aware of the chase tendency so you could be absolutely fine with one. They are a nice size. Friendly. Need cuddles and grooming, regular walks and should be kept occupied.
Go and have a look at the breeder/potential litter?