I did a little investigating of Multi Vendor Marketplace and it doesn't appear that they offer Cash on Delivery as a payment option currently. I'd suggest reaching out the the app developers directly via their support pgae: https://webkul.com/ticket/ for more information. It sounds like they're also quite helpful so they may be able to add that functionality to the app for you!
If you do plan to use COD as your only payment method you will have to pay the Shopify transaction fees on each transaction. Please take a look at our pricing: https://www.shopify.ca/pricing for more information.
Greetings from Webkul!
If the order amount is paid via COD or the payment status is in the “Pending” state, you can choose whether you want to receive the order payment by yourself or you want your sellers to receive the order amount. It depends on the configuration you set in the app.
In case the whole order amount goes to the seller (received via COD), the seller can too send the merchant’s share directly from the app.
Know more about how to manage payment in case of COD: https://webkul.com/blog/shopify-multivendor-marketplace-app-payment-flow/#how-to-manage-payments-in-...
You can set 4 different types of commissions in the app i.e. Global Commission, Seller Commission, Product Commission, Category Commission. To know more, you can request a query here: https://webkul.uvdesk.com/en/customer/login
Talking about the transaction fee in case of COD, As per Shopify reply: They mentioned that, if you enable COD as the only payment method then you need to pay transaction fees on each transaction. Know more about the pricing: https://www.shopify.ca/pricing