The best place for Free-to-play players to kill cows for cowhides is the field northwest of Lumbridge because players may deposit their cowhides and raw beef they obtained with Beefy Bill, who charges a 10% commission. On the downside, cows are more scattered compared to Lumbridge's cow field.
Killing cows can often be beneficial for low-level free players as the cowhides and raw beef obtained can be sold for a decent profit. It also grants combat experience, making it an activity worthy of a new player's time and effort.
To make more money, a player may tan their hides into hard leather and sell it for 109 coins more than a cowhide. A player can also create soft leather which can be tanned for free resulting in a profit of 107. Although it may take more time to tan the hides, the Al Kharidbank is near the Al Kharidtanner and so it is relatively easy to tan hides. If you decide to bank via Beefy Bill, you can use the tannery that is south of Varrock's west bank.