I didn't start reading Sci-Fi at 6, more like around 8 or 9. The local library was my haunt for sometime after that. They conveniently labeled all SF with a atom icon on the spine. After reading every book in the juve section, I went on to find the same in the adult. I remember the librarian starting to question my selections from there until I told her I'd read every SF title in juve.

I think the first bit of SF I can remember reading was an old copy of "Tom Swift And His Rocket Ship". That was in a box of old books in the garage.

After making full use of the interlibrary lending, I finally had to start buying my SF at the local book store. That worked, because SF paperbacks, at the time, were maybe 35 cents ea. Only a small bit more than comic books. SF for a long time was the cheapest read you could get. No longer.