AVN Ads Billing?

Hi,
I want to try AVN Ads but I am a little confused about the billing.
I want to use CPM on a selected website.

Will they bill me monthly or at the checkout?

 

only flat rate ads are paid at checkout.
i don't know when they do billing.

 

What about a max spending a month... is that possible as otherwise it might cost me way more.

 

not month,but max per day.
when you set the ad up you enter the max per day.the max cpm and the max per day can be change any time in your account.you can even pause it if you want.