If you are enlisted in the reserves there is no min wait before you can apply for OCS. As a practical matter you get max benefit of your affliation if you are in the reserves long enough to be observed and evaluated by your division and commanding officers. If they don't know you they will probably write tepid recommendations. As to law school...are you planning on applying for OCS after law school to fly, or some other line officer designator? If you were hoping for a JAG slot they are nearly impossible to get as a law school graduate. Only way to get into the JAG Corps is through the JAG Student Program (no real money, just a guaranteed job). In that case you get a direct commission in the reserves and go to some training in the summer as an officer with pay. During school you are a reserve officer with no pay, no billet and no drills. After graduation you are brought on active duty as a JAG Officer. If you are going for the law degree and then to fly, watch your age. The age waiver for prior service is active duty year for year up to two years. So you get no break as a SELRES sailor with no prior active duty.