If you're talking about making something like this then your biggest problem is getting an incredibly powerful variable speed motor and matching prop. You need a fan that's at least 20 feet in diameter, any smaller and you can't get a steady column of air big enough to lift a person. That fan needs to spin fast enough to move air at up to 150 miles per hour, so the motor you will need will use an incredible amount of power, it's not something you can run on household mains. You'll probably need some kind of three-phase VFD motor since it will need to be variable speed. Although you'll need a properly certified engineer to calculate the motor specifications but probably several hundred horsepower at around 1000 rpm. You won't want to make the fan yourself since if it's just slightly out of balance it will rip its self (and anything near by) apart. You might be able to get something usable out of an old jet engine or other industrial application. Maybe. You'll also need a lot of space, at very least 40 feet of vertical flying space plus the ductwork to recycle the air back around. So a space around 20 feet wide by 70 feet high by 50 feet deep. You'll probably need a heavy duty air conditioner too since friction and pressure will heat up the air pretty fast. After that, it's lots of padding, a trampoline with a wide mesh, a control room and some baggy overalls and you're set.