I agree with Mark on the safety aspect of your endeavor. There are just too many things that can go wrong for a novice to attempt to re-invent something that has been around for a long time.
I work in construction, heavy equipment to be precise and am also a certified crane inspector. When cranes are used for personnel raising or lowering, they must be thoroughly inspected and certified before and during such use.
I understand your desire to save money, we all want to do that, but safety must be the priority. I have red tagged cranes over vehement protests from everyone from project managers to the operator because of safety issues. Once it cost the company millions of $$ in down time. Tough!
Speaking of construction, have you considered looking into the type of elevator used during construction of multi-story buildings? We call them "manlifts", one of those may fit what you want for a reasonable cost.
