In your two photos, the top is an E39, and the bottom is an E46. The "E" codes designate the different development years by chassis style. For more info go to http://www.turnermotorsport.com/html/e_code.shtml
For $17k, you won't find an E39 with 35k mi. You'll have a better chance at finding an E46 for that price and mileage. If I were you, I wouldn't be too overly concerned with finding a very low mileage BMW. Many of them can run reliably upwards of 150-200k mi. What's more important is finding one with the service records intact. This will tell you how well the vehicle was maintained.
As far as reliability, they're no different than other import makes, and you'll typically get more amenities than the others.