Where I can get a free online plan for houses design?

If you go to Builder.com, you will find hundreds of elevations and basic floor plans that you can view and download and print for free. As to free plans, I don't think you will will find very many. Just printing or copying as set of plans is about $50 and I don't think there are many willing to make that big a gift. A set of plans with which you can build a house is about $500 or more for the several copies you need to build.