1991 BMW 735i - No Reverse

Any help with this will appreciated. I am getting ready to purcahse a 735i and it has no reverse. Not really detered by that, but just want to get informed about any repairs or too costly situations. This car drives fine has low miles for year and has not been abused and maintained well. The man who owns just doesn't want the car and will let it go extremely cheap because of this condition. I haven't been able to check the basics(i.e. fluid levels, etc)due to timing. So I was just wondering what else could the situation be or the range of problems. Thanks in advance.