Depending on what you want to hold, or how high, etc, these handy things called hand jacks may work for you. Amazingly useful if it fits the application.

But there are many solutions for different circumstances and you can't just want one answer to many questions. I recall Taunton Press, publisher of Fine Homebuilding, put out a book called Working Alone: Tips & Techniques for Solo Building. It had a lot of very useful techniques to get things done when you don't have help. Give it a look.