A friend of mine is selling a 18x9 wheel, +25 offset with a 245/40/18 tires, will it fit without rubbing on a stock suspension?

If it's a friend, he should let you try them to find out.

Your new wheel will have the following chracteristics:
The clearance from stut housing to the inside of the wheel will be 12mm MORE
The outside edge of the wheel will EXTEND an extra 38mm

Sounds to me like theyre not going to fit real well.

dont ask if they will fit.....make them fit.....roll and pull your fenders and run streched tires ..and maybe some camber....235 or 225 would be the tire size your looking for.. with the 245 you prolly need to work on the roll and pull of fender and camber...the rear would work with pulled and rolled....