from nine or ten years ago on ... for seven years

First things first: I am not a native English-speaker, either.

While it is not incorrect to say "from nine or ten years ago on" (although a well-educated native speaker would likely say "onward," to make more clear the meaning), it is nonsensical to attempt to unite it to the independent clause. A native speaker would be more likely to express this idea with something such as: Beginning nine or ten years ago, for about seven years, I did not work much because I was semi-retired. What makes it more unlikely is that you have a dependent clause (From nine or ten years ago . . .), preceding two independent clauses--the sentence could be said to be too busy. While because is a subordinate conjunction, I was semi-retired can stand alone as an independent clause, as a sentence. It would be better to separate it, and let it stand alone: Beginning nine or ten years ago, for seven years I didn't work much. I was semi-retired. However, adding the subordinate conjunction because to unite the two independent clauses is not wrong, it is not grammatically incorrect. It would be found in speech, but would look awkward in writing.

For seven of the last ten years or so, I didn't work much because I was semi-retired.

Good'n' PUNK