Truth be told, this is not very common in the startups I work with. The more capital intensive your startup is, the more you can and should think about this approach.
Two reasonably common examples of vendor financing in the world of tech startups are equipment financing and development for equity.
Equipment financing is when a vendor of capital equipment, like servers, agrees to sell you their product and takes a loan or a lease instead of cash. We are going to do an entire post on capital equipment loans and leases later in this series and we will cover that in more detail then.
Development for equity is when a third party development firm builds something for you and takes equity in your business (or less commonly, a loan) in return for the development services. It is fairly common for a development partner to take some of their compensation in equity but it is rare for them to take all of it that way. But in this case, a vendor of services to your company is financing your business by reducing the amount of cash you need to lay out to get into business.
In the biotech and cleantech sectors, vendor financing is more common. These sectors have large capital equipment requirements and large third party services requirements. There is a lot of money laid out to third party vendors on the way to cash breakeven and therefore a much greater opportunity to have those vendors finance the business.
When you are starting a company, cash is always tight and so anytime you need a third party vendor to supply your company with services, you should be thinking of vendor financing possibilities. It can be a great way to keep your cash outlays down when the cost of capital is highest.