Not ever sailed a Cal 21, I understand they have a keel lifting set up that's a real pain. I see you'll be sailing on a lake, so it might be something you may want to check out.
All old sailboats keep there value, adding equipment though does not add additional value. If you paid fair market price and you do not destroy the boat, keep it clean, you will recover every dollar you paid for it a couple years from now. So your only cost for using the boat will be the cost of the add ons.