what size studor vent?

I am installing a half bath on the first floor of an elderly friend who is having trouble climbing stairs.. She has an old 3 story home and it would be very tough to run a vent to the roof. I am probably gonna install a studor vent but I dont know if I should use a "Maxi" or a "Mini" or even if an AAV is ok to use.
Can anyone help? .....Thanks Keith

Studor vent

I think that you have to check with the local code office, most codes that I work with will not allow them to vent a toilet; some don't allow them at all. Sorry.