#FORMS.py
class FormCadastroConta(form.ModelForm):
    username = forms.CharField(label='Login',widget=forms.TextInput())
    email = forms.EmailField(label='E-mail do Adm.',widget=forms.TextInput())
    password = forms.CharField(label='Senha',widget=forms.PasswordInput())
    password_check = forms.CharField(label='Confirmação de Senha',widget=forms.PasswordInput())
    class Meta:
        model = CadastroConta

models.PY

class CadastroConta(models.Model):
    user = models.ForeignKey(User, unique=True)

class CadastroLoja(models.Model):
    conta = models.OneToOneField(CadastroConta,primary_key=True)
    nome = models.CharField('Nome da loja',max_length=30)
    segmento = models.CharField(max_length=20)