I build desktop application that is integration between Twitter / facebook/ picasa / (can be others ) on speed (build with c++ not AIR).
It is build first for my use . but then people liked it and started to use it .
Its still in very early beta . before I publish to it to the public . which options do I have to monetize it.
So it can generate income.
The main issue you have is that only 2-5% of the poeple likely to use your application will actually buy it. This is especailly true if you have hot competition like TweetDeck ... just because its better doesn't mean people will swap if what they have is good enough and they are comfortable.
Thus if you start charging people from day 1 you will limit yourself to a very small amount of the market (if any).
So the options you are left with:
Personally I think you are looking at either of the first 2 options, or a combination, advertising on the free, removed advertising for the paid.
Does that help at all?