Another option is to try selling a service or a SAS (Software As a Service). This option is potentially the most lucrative!
The reason for this, is that many services will offer you a recurring commission. Let’s say that you manage to get someone to sign up to a gambling website. Some gambling sites will offer commission on all earnings from that customer for their lifetime with the brand!
Likewise, if you can convince someone to sign up with a hosting account, or to otherwise join a recurring service, then you will often find that you are offered a commission that is paid to you every month that they remain with that hosting company.
Of course, this might start as a small amount of commission. BUT it can then add up to a large amount of time. In a few years, you might have hundreds or even thousands of conversions, which will then earn you recurring income even if your site were to close down!