how much is medium size caravan store & a store built by cement block?.

I have someone who have a permanent site/space to set up a store, now she is considering a construction of cement block store. but I suggested a caravan type because of cost of materia.

a cement store of 9 ceiling with iron door and output corridor, either the door or corridor to have iron protector,

or

a medium size caravan?

what's likely the cost different.

thanks