Heat a paella pan over medium-high heat and add the olive oil. Swirl to coat the entire base of the pan. Add the salt in a circle around the diameter of the pan. This will keep the meat from splattering too much once cooking.
Add the chicken and pork ribs or rabbit (if using) and cook until golden brown. I recommend moving the meat every five minutes for about 20 minutes in total. The browned, caramelized bits that stick to the pan will give lots of flavor to the paella.
Push the meat away from the center of the pan, and add the green beans and cook for about three minutes.
Move the beans to the edge and add the garlic. Sauté for about 30 seconds, making sure not to burn.
Add the butter beans. Sauté very carefully, for about one minute. Be careful not to break/mash them.
Add the paprika and sauté for about 30 seconds and then add the tomato and saffron. Slowly mix everything in the pan together, taking care not to break the beans.
Now add the water. I recommend adding first the 5 cups needed to cook the rice. Then, use a toothpick to mark how far up the water goes. Record this water line. Then add the other four cups. Bring to a rapid boil for about 10 minutes, and then lower to a simmer for another 15-20 minutes. Ideally, at this point, there are only 5 cups of water left in the pan (the amount needed to make rice for 4 people). You can check by using your toothpick. The water line should match the same mark as before -- if it's higher keep cooking, and if it's lower add a bit more water.
Now it's time for the rice! Add the rice to the pan and give a slight stir if necessary to ensure all rice is submerged in the liquid and evenly spread. Cook at a high simmer for 10 minutes, then reduce to a low simmer for another 8-10 minutes (depending on the variety of the rice). You'll know when the rice is ready and the broth is gone, as you will hear a faint ticking/cracking coming from the bottom layer of rice. This crackling means that the rice is caramelizing on the bottom (called socarrat) -- that's a good thing. When you start to hear it, turn up the heat for about 30 seconds (stop immediately if you start to smell burning).
Remove the paella from the heat and cover with a dishcloth for five minutes. Then serve immediately!