I would say that there are actually 3 components that you need as a minimum for your sales funnel, for sure 2 of them.
This would be the squeeze page as first to collect emails of your prospects. Then to provide the freebie from your squeeze page you also need a download page. I would not send just a file per mail to the prospects. Having a download page has several advantages:
when sending a mail with the link to your download page, your prospects learn to click on your links
you can market additional products on this page (like affiliate links of related products)
you can also promote your blog, Facebook page and other social platforms clickfunnels special offer
you can promote other products that you have created (cross promotion)
you can even promote high ticket offers there (like webinars)
So we have the 2 MUST HAVE components of a sales funnel already, the squeeze page and the DL page. Now, the third component you need to actually make money with your funnel is a sales page. If you don’t have an own product yet, you can just redirect your prospects to an affiliate offer. It would not be your sales page in this case, but you have an option to earn commissions and make money.
Or you start to create your own product and keep your prospects in your funnel. That means you redirect them to your sales page after they signed up. If they buy you can even direct them to an upsell and so on, so it’s nice to keep them in your funnel. But do not wait until you have your own product. Go live with your squeeze page and download page and then work on your own product. As soon as you are ready with it, you use your own sales page after the opt-in and put your affiliate product that you have used before on your download page (so you can keep getting commissions). Keep in mind that you also need a download page for your new product you want to sell.
So from the download page we have a link going to the affiliate offer. As long as you keep creating new products (for upsells and downsells) you keep them in your funnel and can always add new products… as soon as you direct them to an affiliate offer (not on your download page but after they buy one of your products) you will “lose” them in your funnel (of course you still have them on your email list).
So in my opinion this are the most important components of a sales funnel that you need to put in place sooner or later. You can always keep creating new things and add them on a later time.