First of all, thank you for putting up this website which is very helpful. I am moving to Palaiseau this September and I saw that RER is the best option to go to Paris City Center. I also saw from your post that they offer weekly passes. Now I'm wondering if they do have a monthly subscription offering. Do you have any idea about this?
Yes for residents you have the option of annual Navigo subscriptions which are discounted usually by a month (i.e. you pay roughly the equivalent of 11 months for 12 months) if you happen to be staying for a long period. You can also go month to month if you're not staying more than a year.
Since you'll be living there I'd recommend you order a new personalized Navigo from Navigo.fr and make use of the online renewal options offered which allows you to avoid renewal lines (which are horrendous at month's end). There's other benefits as well for having a personalized Navigo which you can learn about on the official site linked above.
Best of luck in France,