Stretching is a sign that your plants are not getting enough light. If your plants grow in with too much spacing between the nodes, it leads to tall, weak plants with airy buds, and stunted growth from lack of sufficient light. If you end up with this problem, try to move your lights closer to your plants, careful not to scorch them. If they still stretch, you'll need stronger lights.
What kind of light system(s) do you plan to use?