]] A wealthy respectable gentleman in his mid 30s and with his own estate was certainly considered to be very eligible husband material, even if Marianne can't see herself as the wife.

You are correct that Brandon was quite a catch even if Marianne was blind to his virtues. My great grandmother was over 20 years younger than my great grandfather -- she was 18 & he was 40, a recent widower with four children when they met and married. It was something that was considered entirely proper, especially as "she was pretty and he had money." Today, however, I agree that for a teenage girl to marry a man of 40, or date a 35 year old man, would be a cause for alarm in many families.