are you NUTS!!!!!!!!!!!!!!!!!!!!
I am an engineer working in New York City, i build skyscrapers for a living, with that being said, there are too many variables in this equatation.
1. the soil. (what type is it and where is the bedrock?)
2. the run off of the rain water, where does it normally go, you will have to build drains to deflect the run off away from the shed so as not to undermine any foundation.
3. you must transfer the load out into the slope more, by adding supports to the lower side of the shed, by lower i mean the side further down the slope to transfer the load out more over an area that has no vertical weight and make it share the vertical weight on a horizontal plane.
my opinion is to dig four holes around 12" back from the base of the shed around 36" deep and 8x8 wide and place one piece of 6x6 "H" iron with a flat 1/4" piece on to top to with in four inches of the bottom of the sheds floor base and fill each hole with concrete.
go to the front of the shed and dig four 8x8 trenches out from the front of the shed into the flat area where ther car is pictured around 8 feet that line up with the holes at the back.
put a layer or rough stone about 1" deep and then 2" of concrete with reinfrocing rod horizontally through it.
then get four pieces of 4x4 "H" iron and run them from the supports at the back all the way through to the trenches at the front.
your shed is then indepentley supported by the eground with two good bases sharing the load over a much wider area with the weight being transfered horizontally front to back and THEN vertically down through six supports.
If yoiu waant then you can take out the wood supports and lower the shed down onto the steel, no welding, even an amature could do this for $500 and a few weekends with a friend to help.
just dig a few rough drains along the front going down the sides of th eshed about 36" to each side, place heacy duty polythene in them with stones on top and they will take all rain water away to stop erosion.
any questions email me back