Thanks for all the answers, guys but I was asking HOW to logistically set up a 30 day minimum stay. For anyone else looking to accomplish the same task, here is what you do:
Go to Your Listing and then click on Accessibility Settings at top right of page. Then, Reservation Preferences, where you can alter the minimum number of days you requrie. Under pricing, you can set custom monthly prices for each month or just establish a discount to your daily rate, even though no one will see your listing if they're wanting to book shorter than your established minimum.
I've noticed that more and more hosts all over the country are requiring 30 day minimum stays due to imposed City regulations. It's not ideal but it works just fine here or on other sites. I just booked 3 months in Santa Fe. No problem.