Kill greater monsters within the Forinthry Dungeon, use rune arrows. 100k gp/hr, plus it's the best range of OSRS gold xp for freeplayers I've heard of. I believe that air runes are priced about 200k/hour on the 66 runecraft. Of course, the higher the level of runecraft is, the higher. In the ideal scenario, you could purchase a bond and earn money using one of the methods for members, assuming you play one hour a day and already have decent stats.
Comments, tweaks or other things
While I'm not sure about the money-making of members, this is some freeplay stuff. Kill Hill Giants are found in Edgeville's resource building. Grab the limpwurt roots and bones. ~250k gp/hr last Summer. Run through the mud of keys towards the Lava Maze and only take the most valuable items (you should not consume anchovy pizzas). This is one of the most effective way to earn money from f2p, I think about 400k/hr if you're good however muddy keys can require a while to purchase.
Mine adamant ore. I love to buy RuneScape gold mine this in the hobgoblin mine. Wear the full batwing and shield, and you won't need food. Hop worlds. It's not common to see PKers in the area. Superheating can also be done through mining coal. This can prolong your travel time but I'm not sure that it's better. 70 miners are required. 70 smithing is necessary when you're superheating. 200-300k gp/hr.