I have affiliated for free with two internet groups who said I will be earning by just inviting more people to the site. When these people buy or order products I will have commission. Later on they require me to upgrade in order to earn. Upgrading means I have pay a certain amount per month. Is this not a harms way?

It sure is and this is how affiliate programs work. They offer nothing except hype and expect you to pay. It very similar to pyramid selling. All the money goes to the top. Start your own business on the web and that way you will make the money.