there are 3 different models to do this (i admit, i was thinking to do this with some of my sites in the past):
1. you charge for access to your linklist: this should not be a problem at all as submitters must agree to your tos anyway. the content and everything is hosted on the "free" site as normal. What you will get is very high quality traffic from submissions and the ll/tgp owner probably will loose a lot of traffic.
2. you keep your site as usual, but use a gateway between the link and the free site/gallery. here you charge for gallery access. this should not be a problem if you use a textlink. but it probably can be a problem if you are using thumb previews. However, what you will get is that the linklist will not loose as much traffic as in (1.) and you could use clever marketing like tgfind who let you see 3 samples and then asked for email (in 2001) or payment (after 2001). this is probably the sort of thing most of you are thinking of as a good model.
3. (not a real option) you load the content from your site or in frames like some tgps/lls do. this is a problem anyway whether surfers pay for access or not.
yes, this is what i consider the avs model.
the access to the galleries/free sites could be managed by each ll/tgp individually or by a 3rd party system, which would be 4rth party processing then (eg the system was using ccbill).
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however, if established it would not have serious consequences for free porn.