One bedroom apartment, 14th floor with one toilet. Toilet and bathtub in one room, vanity outside next to the toilet wall. I will like to relocate vanity and use the space to add a second toilet, but will need to connect it to the existing toilet's drain. Can I find a double toilet, side by side or back to back in order to do this?

This is doable. However it would involve tearing up the unites ceiling and making a mess of their bath to change over the piping. Do you have the Condo Board and the owners permission to do this?

Can I find a double toilet, side by side or back to back in order to do this? You don't need a special toilet but be aware that this will be a major remodel job that will require a permit and everyone involved permission. Good luck. Tom