[Pontiac]

A trader would not be able to afford galley slaves for rowing

Here is a link for different Greek ships

http://www.hellenicaworld.com/Greece/Technology/en/Ships.html

The ship was probably a single masted sailing vessel for economic travel

[Reily]

At least in the Athenian Navy the rowers were free men. Men of the lower classes who couldn’t afford the hoplite panoply but free men. Very well trained, expert towers who could maneuver the Athenian ships like human powered torpedoes, as the Persians discovered.

See

https://www.amazon.com/Lords-Sea-Story-Athenian-Democracy/dp/0143117688/ref=sr_1_1?ie=UTF8&qid=1534000896&sr=8-1&keywords=Athenian+navy