add managed resources section

Author: craigshoemaker

articles/container-apps/vnet-custom.md

@@ -5,7 +5,7 @@ services: container-apps
 author: craigshoemaker
 ms.service: container-apps
 ms.topic:  how-to
-ms.date: 1/28/2021
+ms.date: 2/3/2022
 ms.author: cshoe
 zone_pivot_groups: azure-cli-or-portal
 ---
@@ -67,6 +67,10 @@ To create an internal only environment, provide the `--internal-only` parameter
 
 ::: zone-end
 
+## Managed resources
+
+When you deploy an internal or an external environment into your own network, a new resource group prefixed with `MC_` is created in the Azure subscription where your environment is hosted. This resource group contains infrastructure components managed by the Azure Container Apps platform, and shouldn't be modified. The resource group contains Public IP addresses used specifically for outbound connectivity from your environment as well as a load balancer. As the load balancer is created in your subscription, there are additional costs associated with deploying the service to a custom virtual network.
+
 ## Example
 
 The following example shows you how to create a Container Apps environment in an existing virtual network.