How to set permissions for an inherited User model from AbstractBaseUser with Django restframework

Question

lets have a structure of my User model.

BaseUser <- BusinessOwner <- Business Staff (BusinessOwner can create,update,delete BusinessStaff )
BaseUser <- Customer

I'm having problem when creating an inherited user from AbstractBaseUser, All i want is to add a row in myappname_baseuser_user_permissions table which has columns : id , baseuser_id, permission_id, with correct permissions assign to correct user id, such as : add_staff, change_staff, delete_staff

Things is normal when i create new BusinessOwner user with admin page and easily add permissions, but not the POST method im using with django restframework, there are no permissions. So where should i put my permissions code? and what is the code? in model.py or view.py ? ,my permissions codename are : add_staff, change_staff, and delete_staff

here is my model.py:

class UserManager(BaseUserManager):
    def _create_user(self, email, password, is_staff, is_superuser, **extra_fields):

    now = timezone.now()
        if not email:
            raise ValueError('The given email must be set')
        email = self.normalize_email(email)
        user = self.model(email=email,
                is_staff=is_staff, is_active=True,
                is_superuser=is_superuser, last_login=now,
                date_joined=now, **extra_fields)
    user.set_password(password)
    user.save(using=self._db)
    return user

    def create_user(self, email, password=None, **extra_fields):
        return self._create_user(email, password, False, False,
                             **extra_fields)

    def create_superuser(self, email, password, **extra_fields):
        return self._create_user(email, password, True, True,
                             **extra_fields)

class BaseUser(AbstractBaseUser, PermissionsMixin):
    first_name=models.CharField(max_length=20)
    last_name=models.CharField(max_length=20)
    email=models.EmailField(max_length=254, unique=True)
    is_staff = models.BooleanField(default=False)
    is_active = models.BooleanField(default=True)
    date_joined = models.DateTimeField(default=timezone.now)

    objects = UserManager()

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = []
    class Meta:
        verbose_name = _('user')
        verbose_name_plural = _('users')



class BusinessOwner(BaseUser):
    business_name=models.CharField(max_length=20)

class Customer(BaseUser):
    address=models.CharField(max_length=30)

class Staff(BaseUser):
    position=models.CharField(max_length=30)

my view.py

class CreateBusinessOwnerView(mixins.ListModelMixin,
              mixins.CreateModelMixin,
              generics.GenericAPIView):
    queryset = BusinessOwner.objects.all()
    serializer_class = CreateBusinessOwner

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

    def post_save(self, obj, created=False):
        if created:
            obj.set_password(obj.password)
            obj.save()

and my serializers.py

class CreateBusinessOwner(serializers.ModelSerializer):
    class Meta:
        model = BusinessOwner
        fields = ('email', 'password', 'first_name', 'last_name', 'business_name' ,'date_joined')
        read_only_fields = ('date_joined',)

Thanks for helping me!