My pal got two immaculate insulated & stainless steel inside ) 20 foot shipping deep freeze containers that hard side and rear doors for just over £ 450 each ten years ago .
The freezer gear had been taken out but they made fantastic honey prep rooms one for extraction , melting wax and making foundation soaps, the other for bottling & making mead9 non retail ).
So I'd also try and see if any second hand shipping containers are available as well.