Ads for unregistered users?

I’m thinking of adding google adsense ads for unregistered users only. I generally don’t like ads but after reading multiple posts and websites the following points were brought up. Only unregistered users will see ads, contributing registered members won’t be affected. It’ll encourage unregistered users to log in. And lastly, even if a forum is non profit it costs money to host it.

I personally don’t care about paying hosting fees but what I really would like is to upgrade these forums to Vbulletin 4, or at least 3.86. It would allow me to remove multiple plugins I’ve had to add and make this site a bit more stable and increase the longevity of it. Along with the upgrade the forums would also regain full vbulletin support. At the moment I have to google search for hours to find some obscure plugin hosted on some warez site. In the process of doing this I also have inadvertently received viruses and the whole process is just a pain.
As soon as I get enough money to buy Vbulletin support I will remove all the ads.
Anyhow tell me what you think.

Alright I’m going to go ahead and test this out to see if it works well. Hopefully I can raise enough funds to upgrade

Shouldn’t be a problem. Lots of forums do that for unregistered or non-subscribed viewers.