Horrible idea. Not recommended at all. Solution is not sterile and can cause multiple types of infections.
That is a bad idea. You increase your risk of an eye infection. It is not worth it.
Horrible idea. Contact lens solutions contain water, cleansers, preservatives and other chemicals that have been rigorously tested to ensure that they do not harbor infective organisms. Home solutions cannot be made to the same standards. The risk of vision loss from infection is too high to bother trying to save money. You would be better off switching to glasses instead.