I wish to add a recepticle in my utility shed. I now have a light fixture and a switch controlling the fixture. The power source goes to the fixture, and one cable goes to the switch. Question: Can I access power for my new recepticle from the switch, or must I go to the light fixture? How do i connect.

You all have been so helpful in my basement remodel (passed inspection and am in the process of drywalling :D ) that I thought I would pick your brains on a question for my daughters soon-to-be new home. She is looking to buy a spec home and the standard electrical the builder installs is 100 Amp. This is a relatively small home (<1000 sf) with gas heat and gas water heat. But I suggested she upgrade to 200 amp just because it would be so much more expensive to do in the future should she need it. Cash is tight but it's only $200 more. Am I on the right track here or is 100 Amp OK for a smaller home? Thanks in advance!!