heater fan problem

Hi all , I am looking to buy a renault laguna diesel estate 2000 reg, the only fault with it is that the fan selector slips back to hot all the time, can anyone tell me please is this a big problem , before i go waste my little bit of money??? because apart from that it is a really nice car,.and I only have until tomorrow night to make my mind up , so advice would be gratefully accepted, thank you