Did Franklin was to work in his father's trade? What was it?

No, Franklin disliked candle-making. I'm not so sure his father like it either, but he couldn't make a living dyeing, so he did what he had to in order to support his family. 

At ten years old I was taken home to assist my father in his business, which was that of a tallow-chandler and soap-boiler — a business he was not bred to, but had assumed on his arrival in New England, and on his dyeing trade would not maintain his family, being in little request. Accordingly, I was employed in cutting wick for the candles, filing the dipping-mold and the molds for cast candles, attending the shop, going of errands, etc.

I disliked the trade, and had a strong inclination for the sea, but my father declared against it.