I inherited a metal shed that was used as the allotment site's tool store.
Without exaggeration you could pop it open with a tin opener.
Luckily my site hasn't suffered much from n'eer -do-wells.
Possibly the road workers huts were made from thicker material but essentially anyone determined can get into your shed - old / cheap tools on the plot is my advice. Many don't lock their sheds so that if they get robbed at least the door remains undamaged.
Condensation is a well known problem with metal sheds.
I'd just consider the shed on the plot to be something that keeps the rain off you and (possilby) the rain off you old/cheap tools.
I had two years use out of a shed made from pallets - did the job...
Pip pip,
Balders