class CustomerUserProfile(models.Model):
    user = models.OneToOneField(User, blank=True)
    # Only little extra information need, eg, Full Name

class MerchantUserProfile(models.Model):
    user = models.OneToOneField(User, blank=True)
    #More extensive info. Full Name, Address, Contact Info, Payment Details, URL

##### OR ######

class UserProfile(models.Model):
    user = models.OneToOneField(User, blank=True)

    is_Merchant = models.BooleanField()
    #Further information here
    #Even a function to perhaps check all the information is checked in correctly.