Most businesses require startup fees as well as a cash flow to finance the products being sold. However, affiliate marketing can be done at a low cost, meaning you can get started quickly and without much hassle. There are no affiliate program fees to worry about and no need to create a product. Beginning this line of work is relatively straightforward.
Always disclose your affiliate relationship. Most visitors will probably understand that graphic ads will lead to your getting paid, but if you write a review or use an in-text link as a recommendation, you want your readers to know that may lead to compensation as well. This ensures you retain transparency and trust with your readers, but also, it's required by the FTC's endorsement rules.