asp.net mvc @Html.CheckBoxFor dynamic

using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Web;

 namespace CorePartners_Site2.Models
 {
public class CareerForm
     {
    //....
    public List<CheckBoxes> EmploymentType { get; set; } 
      }
 }

 public class CheckBoxes
 {
     public string Text { get; set; }
     public bool Checked { get; set; }
 }

and added at my form

@Html.CheckBoxFor(model => model.EmploymentType, new { id = "employmentType_1" })
@Html.CheckBoxFor(model => model.EmploymentType, new { id = "employmentType_2" })
@Html.CheckBoxFor(model => model.EmploymentType, new { id = "employmentType_3" })

CheckBoxFor takes a bool, you're passing a List<CheckBoxes> to it. You'd need to do:
@for (int i = 0; i < Model.EmploymentType.Count; i++)
{
    @Html.CheckBoxFor(m => m.EmploymentType[i].Checked, new { id = "employmentType_" + i })
    @Html.HiddenFor(m => m.EmploymentType[i].Text)
    @Html.DisplayFor(m => m.EmploymentType[i].Text)
}

Notice I've added a HiddenFor for the Text property too, otherwise you'd lose that when you posted the form, so you wouldn't know which items you'd checked.

Edit, as shown in your comments, your EmploymentType list is null when the view is served. You'll need to populate that too, by doing this in your action method:
public ActionResult YourActionMethod()
{
    CareerForm model = new CareerForm();

    model.EmploymentType = new List<CheckBox>
    {
        new Checkbox { Text = "Fulltime" },
        new Checkbox { Text = "Partly" },
        new Checkbox { Text = "Contract" }
    };

    return View(model);
}