How is money created on net? I have the impression that everyone has more net money than in the past. By net money I means cash + money lent to others - money borrowed from others. If this is true, where does the extra net money come from? Is it right to say that originally all the extra net money comes to the world as interest paid by the central bank for the reserve deposit of commercial banks?

I read that commercial banks create money by making loans. But when one person borrows money from banks, his net money doesn't increase. And when people make transactions, money just goes from one to another. How does it come that finally everyone has more net money than before?

Edit:

I have a second thought that my impression is simply wrong. It's only true to say that generally everyone is wealthier than in the past. If we look at the richest businessmen in the world, their "net money" as defined above can often be hugely negative, but they are still wealthy since they possess a lot of other things like buildings, factories etc.

And besides those business men, the "net money" of the government is also hugely negative(almost every country's government has a large public debt). So if the "net money" of the popluation as a whole remains more or less constant(in the spirit of "loans + cash == liability deposits" mentioned by @Lumi), a few entities having hugely negative "net money" make others's net money increase, so one could have the impression that the "net money" of the majority of the population has increased.
Suppose I define "net appliances" as dishwashers plus appliances lent to others minus appliances borrowed from others.  

Suppose I build a refrigerator and lend it to you.  Then your "net appliances" have been reduced by one, my "net appliances" have increased by one, and the total of the world's "net appliances" has not changed.

On the other hand, the world does now have one more refrigerator, which suggests that "net appliances" was never a very interesting notion in the first place.