Add the website error details the first time the app is run

Provide further details about the website error that is thrown the first time the app is run.

Author: ardelean94

16/umbraco-cms/tutorials/starter-kit/install-the-starter-kit.md

@@ -59,4 +59,9 @@ To install the starter Kit via Visual Studio, follow these steps:
 
 You now have a fully functional Umbraco site with demo content, templates, and structure to explore. Use this setup as the foundation for the upcoming lessons in this Starter Kit tutorial.
 
+{% hint style="warning" %}
+If `Umbraco:CMS:Runtime:Mode=Development` and `Umbraco:CMS:ModelsBuilder:ModelsMode=SourceCodeAuto` or `SourceCodeManual` will cause an error on the website for the first time the app is run.
+To fix it log into **Umbraco Backoffice**, go to **Settings** -> **Models Builder** and click on **Generate Models** button. Restart the app and the error should be gone.
+{% endhint %}
+
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