To make avocado oil, how ripe do your avocados need to be

Depends on if you'll buy for instant consumption or for storage.

If you want to eat/prepare them right away, you want an avocado that feels soft on the inside, when pressing them they will cede and have that soft feeling ripe avocado has. It shouldn't cede very much though, as those are past their prime. The very good ones even smell in a nice avocadoey way a bit (or maybe that's just my insanity.)

If you want to prepare them later, you want firm ones that cede only a tiny little bit (the rock hard ones mostly never ripen in my experience,) you then store them in a porous bag (the typical brown paper bag or a newspaper) to let them ripe. To speed up the ripening, you can add an apple to the bag.

See also this related question

The cold process is easy.Just blend the fresh pulp using a kitchen blender to make a thin and smooth pulp.Heat the pulp in low heat and maintain a 50 degrees celcius heat for about an hour and a quarter.This is called malaxation which enables the oil molecules to collect into globules visible by eye.Then after malaxation,take the warm malaxed pulp and strain it into a cheese cloth or a muslin cloth and press by squeezing out the oil as it collects into a container beneath.There you have pure virgin avocado oil.I never buy cooking oil at home.I use this for deep frying,baking and desserts making.Its very health and pocket friendly cooking oil especially if you live where avocado is grown in plenty like my home area of Meru in Kenya.I have 20 avocado trees which i make use of.You can try this too at home and enjoy your cooking.