Create a ninja form with a template called Create Invoice/Quote with required mapping fields. Go to Emails and Actions tab of the form and enable Create Invoice or Quote action. Click on the settings icon to map the fields and select type Invoice or Quote you want to create and then publish the form. Email is the required field for creating an invoice/quote.
When user request quote or invoice from ninja form, admin can add items to the quote or invoice later and send it to the user for payments.
If the email address submitted in the form is not already linked to any customers/users then this addon will automatically create a new customer with this email.
Once you have above plugins installed and activated, you need to create form with following fields and map them in the gravity form feed page.
* Customer Email
You can also use the following optional fields for getting more data for invoice or quote:
* Customer Name
* Customer First Name
* Customer Last Name
* Business Name
* Zip Code
* Phone Number