I am not a teacher.
I'm afraid it isn't.
The first sentence can only start with "However," if there is a preceding sentence saying something contradictory and leading logically to this one. (This may be the case, but I don't know that.)
You don't support your livelihood, your livelihood is what supports you.
The second sentence has many errors in it; you should try again.
The third sentence is not too bad.
I personally find it rather irritating to read a series of sentences that start with adverbs, but that is a question of style.