You have to look for regularly in the service board, as there are very few campaigns allowing brand new members.
I find no campaign for now that is accepting newbies for their signature campaigns but he can try to join some social media campaigns and as well as some signature campaigns here;
The good news is that you can be junior member in almost no time.
Not in no time but he needs to wait for a month and a half for him to rank up as a Jr. member and he needs to wait for that time so that he can now join some campaigns.
No, as I remeber, it only took one month, because the first 14 activities are given at once.