How to set up an internet access point for visitors?

I am involved in a group in Germany which are providing assistance to asylum seekers.

One member of the group suggested that an inteet access point be provided in the temporary accommodation unit to help visitors to stay in touch with family etc.

Whilst this is certainly a useful feature, I see legal issues should the service be misused.

I assume that some kind of registration would be necessary to be able to identify users should problems arise. Also, some kind of filtering (e.g. no YouTube) is necessary to avoid a few users from taking all the bandwidth.

Does anyone have any experience in setting up such a system? Is it do-able on a tiny budget?