(from a post made by Ted Wang in May 1997)
...Possibly. I also believe that they might be into organized crime. If you ever see the houses those Mafia families have in New York you could see how I came to this assumption.
Also these indidviduals are often regarded as pillars of the community. Al Capone played a large part in the law that now requires milk to be dated so that "the children don't have to drink sour milk." Mainly their presence keeps most two bit hoodlums out.
You could never tell just by watching them at home if they were really criminals.
Who knows what else Happi steals using the panty robberies as cover? That's the REAL reason Genma and Soun want him out of the picture. So they can become The Don.
Consider the property damage Ranma and Co. cause to the neighborhood under what appears to the outside observer as collateral damage from their fights. How do we know that certain areas didn't pay their insurance - and then accidents happen?
Notice nobody has ever pressed charges because of the intimidation the Tendos hold on the area. With enforcers like Ranma and Akane - step out of line and they'll crush your skull with a run by malleting.
Ryouga never has to go through customs. What kind of contraband can be hidden in that backpack of his?
There is a gambling ring operated by Nabiki in the school. In most places gambling's illegal.
It has been pointed out Genma has criminal tendancies.
What is the REAL reason Gos takes so many photos of Akane and company? Perhaps, surveilance?
The marriage between Akane and Ranma could be to unite the Saotome and the Tendo crime families for the purpose of bringing down the Kunous! In Punisher: The Movie the head of the Japanese crime syndicate was a woman who when she was first intiated proved her loyalty by poisoning her brother with a bowl of rice! Akane's bad cooking, everything Kodachi makes. For sure we know the wedding was a big event. If you've ever been to an Italian wedding they really party! Sure this is all speculation, but it would explain the well-off economic situation without any apparent income. In the real world, the FBI puts surveillance on people like that.