For us, in this sort of situation, a shipping container is the best option. They're considered to be a 'temporary' structure (like scaffold,) so their value is not added to your Rateable Capital Value and no permit is required.
I recently bought two new ones (20 ft x 8 ft,) for $6000 each landed. I couldn't have built a comparable shed for that sort of money, what with permits, site inspections, building inspections, neighbours' approvals, drainage from downpipes, concrete foundations, (and foundation inspections of reinforcing steel placements,) and so on and on ad nauseam...

They were packed full with goodies (each weighing around nine tons,) at Rock Bottom (our current abode,) and are at present sitting outside my shed at Our New Selection (our future abode,) awaiting the shed reaching the lockable stage. They will then be emptied and returned to Rock Bottom to be filled again.
And they're secure. It would take a well equipped and determined scumbag to break in to them.
And when I've finished shifting I can sell them and recoup my money, or retain them for use as garden sheds.
The 'pros' far outweighed the 'cons'.
Win/win.
Quod erat demonstrandum.