Well, there are some negatives: BMW is a trademarked name, and there are a lot of WIPO cases where the company went after domains with bmw in them. Argueably, most started with the word "bmw." However, a site like bmwforum.com has been operating since 2000. It is owned by an internet portal business apparently. So if that site can exist, I think yours could too. Undeveloped, I'd say the domain is worth anywhere from $50 to $300.