What all is involved and how much would it cost to give my mom a place of her own?

I want to have a mini cabin, or something the like, put here on my property for my mother to live in, approx. 12 ft x 16 ft. How much should I expect to pay to have an area approximately 20 ft wide x 75 ft long leveled and graveled? What if I purchased a cedar storage building from Home Depot and put a foundation down for it and had it insulated and wired for heat and lights? I would wait on plumbing and would have it added later. Is someone out there that can advise me what all is involved and how much would it cost to give my mom a place of her own?