IP... Just downsize your original build.. a lot.. but plan 'expansion' into every piece of lumber installed...
It's costs 'nothing' but a couple weekends, to get out your shovel and start prepping the pad...
Even though you might not be able to afford running a sewer line and electrical and water to it now, you can certainly run those things just outside the pad.. and connect to them later...
A hose across your yard can be temp installed to run water.. until you can afford a proper sewer line, you can dig a 2 foot round by 3 foot deep pit and fill it with pea gravel and run your short sewer line from in the shed into it for general stuff from the sink... (IOW, no peeing)
There's an age old riddle.. Question "How do you eat an elephant"... Answer: "One bite at a time"
You can do this.. All it takes is ten sacks of concrete here.. ten there... six 2x4's here'' six there... before you know it.. there's a 'shell'.. then you're off and running...
If you had invested 25 dollars on materials and 4 hours a month on it since you first started this thread, you'd easily have the building itself raised by now.... and probably a lot more...
That which is as rest, tends to stay at rest.. and that which is in motion tends to stay in motion... It's basic physics.. just 'get in motion'... The rest will work itself out....
BTW.. this thread has some of the best potential tag lines of any on this site...