The habitable planets will be very similar in size to earth and are on separate orbits orbiting a Sun-like star exactly the size of our own Sun. How many habitable planets can I fit into the habitable zone of my star and still stay stable for millions of years, without the orbits intersecting due to gravitational interaction?
Given our solar system as a model, you could fit three of them, jackpot!
Venus was a very unlucky planet -hypervolcanic activity, perhaps connected to the mechanism that inverted its rotation helped create its hellish atmosphere. But without those factors, it could really be a tropical paradise.
In Mars' position, you could throw in a planet with just enough mass for the core to rotate nice and strong, have your gravity and magnetic field protecting the atmosphere and voilà! A little cold but definitely inhabitable.
Overkill: A binary Earth and that would make four planets good to call home
I wrote an extensive series of blog posts to answer this question: https://planetplanet.net/the-ultimate-solar-system/
Jumping to the punchline -- based on orbital stability alone it is possible to pack several hundred planets in the habitable zone of a single star (see https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/).
(Or a million if you incude a supermassive black hole: https://planetplanet.net/2018/06/01/the-million-earth-solar-system/)
Systems that are more likely to form naturally can easily have up to 5-10 worlds in the habitable zone.
Happy to answer any other questions on this. I've found that it helps people to trust me to mention that I'm an astrophysicist and orbital dynamics is my specialty.