That's a good car... with an undercarriage inspection of course.
Well, it might be a good car. Or it may have structural rust (which makes it a less-good car). Being stored in a carport in Santa Cruz isn't healthy for rust-prone cars like the e9; the term "rust-free California car from a dry climate" doesn't apply in Santa Cruz.
But as dang suggests, have a body man skilled in vintage car restoration (*) have a look at the car, with emphasis on the underside and upper spring mounts. If it checks out in these areas, its value goes up quite a bit; if not, then it probably will become a parts donor.
*) Many automotive autobody shops and technicians know how to perform collision repair on 21st century Toyotas, but have no idea how to repair a car from the mid-20th century. Not that this makes them bad people; it's just that they won't be able to assess what it would take to repair your father's BMW. So find someone who regularly restores older cars, not necessarily BMW's, though that would help.