How does your pet site generate revenue?

Account upgrades seem to be the most popular revenue generator for pet sites these days. If they don’t have account upgrades, they may have a cash shop. Additionally, some of them may also run advertisements to generate extra revenue.
 
There are various ways a virtual pet sites can generate revenue and that could be through various methods, including account upgrade, advertisements, sponsored content and affiliate marketing.
Affiliate marketing could work for pet sites if they have their forums opened to the public and they implement the amazon affiliate ad company. It could help them monetize the forum and earn extra income, however, I wouldn’t recommend using it for users if they already have regular advertisements on the site.

 
Affiliate marketing could work for pet sites if they have their forums opened to the public and they implement the amazon affiliate ad company. It could help them monetize the forum and earn extra income, however, I wouldn’t recommend using it for users if they already have regular advertisements on the site.

Yes, I understand this clearly because there would be a conflict of interest if it's done that way. What is the best ads network to use and what other ways I can generate substantial income on a forum.
 
What is the best ads network to use and what other ways I can generate substantial income on a forum.
The best way to generate income form a forum is by selling ad space and membership, however, this will work only when you have a lot of activities and a lot of traffic.