public class ProductVM
// This is the main viewmodel for the view
{
    public int Id { get; set; }
    public string Title { get; set; }
    public List<ProductPropertyVM> Properties { get; set; }
}

public class ProductPropertyVM
// This represents a property a product can have, e.g. "Colour".
{
    public int Id { get; set; }
    public string Label { get; set; }
    [Required]
    public int? SelectedRadioOption { get; set; }
    public List<ProductPropertyOptionVM> Options { get; set; }
}

public class ProductPropertyOptionVM
// This represents options a property can have, e.g. "Red", "Green", "Blue".
{
    public int Id { get; set; }
    public string Value { get; set; }
}

for (int i = 0; i < Model.Properties.Count(); i++)
{
    <strong>@Model.Properties[i].Label</strong><br />
    @if (Model.Properties[i].Options != null)
    {
        @foreach (var option in Model.Properties[i].Options)
        {
            @Html.RadioButtonFor(m => m.Properties[i].SelectedRadioOption, option.Id, new { id = "" })
            <span>@option.Value</span>
            <br />
        }
        @Html.ValidationMessageFor(m => m.Properties[i].SelectedRadioOption)
    }
}