The requirements of this method are high but it’s only really the smithing requirement that is difficult to achieve. You will need 85 smithing to smelt rune bars, a skill that is required for this money-making method. You will also need 43 magic to cast the superheat spell and 35 dungeoneering and mining for a coal bag. You will also need to purchase rune ore and nature runes to complete this method making this method requiring some starting cash to continue.
Become a dog walker if you live in an area where they are in demand. You can walk dogs for people who own dogs but who are too busy to walk them. However, this can be a demanding job, especially if you end up walking a few dogs at once or if you are walking dogs throughout the day, so ensure that you have the physical stamina for this type of job.