I realise that can't be answered without me saying how serious the corrosion is. The context is that I'm looking at a 2004 Ford Focus on eBay and the MOT history on the DVLA web site reports an advisory at the last MOT six months ago:
O/S REAR INNER SILL IS RUSTY
None of the previous MOTs reported any corrosion, just the usual headlight bulbs, brake pads worn, etc. The last MOT just states the above in the Advisory section without any more detail.
Aside from the corrosion problem the car looks exactly what I want. I suspect the car will sell cheaply as there doesn't seem to be much interest in it, so I don't mind paying for the sill to be fixed as long as:
it doesn't cost a fortune
it isn't the start of massive bodywork problems
So what I'm hoping you can tell me is whether sill corrosion is fairly routine on 13 year old Focuses and easily fixed, or whether it's an ominous sign and I'd be well advised to walk away.
I don't have the kit (or skill) to fix it myself, so I'd be paying my friendly mechanic to do the work.