Using pre existing long oak (wood) cupboard as lower kitchen cabinets?

Need some advises. 

So i been thinking, instead of spending money during renovation to make those same same looking kitchen cabinets, why not just go buy something i like .. a long side wood cupboard will fit the dimension and needs easily. 

mmm, so why is this not an idea i should go ahead with? 

oh yah, for the sink and cooking hob, i was thinking of fabricating a cement concrete support beside the cupboard . if beside hob, will it be a fire hazard , as compared to those kitchen cabinets my contractor will make ?