Hi Henry,
How many sq. ft do you think you will have?
and what are you thinking for shape, square or rectangle?
with a hoist and a 4 post lift side by side you can have space for 4 cars temporarily and 3 cars at all times.
Don't forget about lighting either, I'm a lighting nut...

...lots of roof lighting, some windows for natiral light, and the newish wall lights just over waist high.
Nicely finished concrete floor, epoxy painted white or very, very light grey, sloping slightly if possible to make clean-up with a waterhose & soap and squeegee work easy and draining a snap. A flat entrance way/driveway to make pushing cars in & out for pressure washing possible with one person.
Those are the basics I would consider. Then you can expand on those ideas to include a heavy tool area, heavy duty room, etc.
Regards, JRV