Roadmap members can use the standard customer accounts to create two payments of payment settings.
Cash Payment Customers
These customers can be tagged as "Trade" users, and Standard payments where customers add items to their cart, and move through the checkout like any other customers.
Invoice Only
The invoice only flow can be configured on a using the metafield "Draft orders only". Once set to true, this logic will allows the user to shop using the cart the same as any customer, however, the checkout button text in their cart slider and cart page will change to say "Submit Order".
When a user clicks this button, they will be taken to a success screen which display a success message of your choosing.
At this point, the order will appear in the Draft orders area of your Shopify order admin.
From here, you can trigger and invoice to be sent that user.
Does this only work if I have a DTC vs Trade customer setup?
No - there is nothing stopping this feature being setup for any segment you desired - this is because the trigger that controls the checkout flow is configured by a metafield on the customer profile, and therefore brands can add this to any users these wish.