Is it different for renting vs buying?

We rent a 2 bedroom apartment right now that is just over 900 sq ft. It fits us as a family of 3 pretty well and we could potentially fit another child if need be. I would never purchase a home less than 1400 sq ft though. But for rent, I prefer 900-1000 sq ft as my minimum.

We're looking into moving into the city and we definitely couldn't afford a place any bigger than our current amount of space. I did just see an apartment in a very desirable area with the top rated schools in the state but it's only 500 sq ft! I couldn't imagine living in such a tight space.

What is your minimum?