Research on Niche and find affiliate program that free to join. Many company offers free affiliate.
Use free marketing platform such as blog, youtube, social media to promote affiliate products.
Use email marketing to reach out your community and personal network to promote affiliate products.
Create useful content for users and SEO to drive organic traffic on your affiliate blog.
Join online forums and discussion group related to your niche and submit affiliate link
Utilize influence marketing to reach out influencers in your niche and promote affiliate link.
Use whatsapp community and telegram channels to share link and affiliate website.