Will I be charged for a full month of membership during my first month?

No, you will only be charged for the pro-rated amount of days left in the month. For example, if you sign up for an individual membership ($85/month) on June 20, you will be charged for your Initiation Fee plus the pro-rated monthly dues of $28.33 ($85 / 30 days = $2.83 per day X 10 remaining days in June).