The cost of concrete

Ahhh?
No footings and a slope.
Dude you need to talk to someone in your area that does concrete for a living. Not your neighbors slack jawed cousin.
Buildings that set on top of a concrete slab need structural support, ie footers.
You dont want to spend the money and end up with a piece of crap.
I have built several shop and storage buildings, do it right or dont do it.
Manufacturing of the building does not require footers