Permanent party is pretty much a way to get to an ATC six months earlier than getting there on regular work release. An inmate is eligible to apply for permanent party when he/she is 32 months short, whereas they would not be eligible to apply for work release until they were 26 months short. As Mah indicated, permanent party residents are accepted under cooking or maintenance assignments. When filling out the initial request paperwork, it is important to stress one's prior experience in either one, or both, of these areas. This will increase the chance for acceptance.
Permanent party inmates sign a six month contract for work at the ATC. After this contract is up they automatically transition to "regular" work release and are then eligible to work in the community. (Sometimes they are even allowed to get a regular part time job while in their fifth month as a permanent party as long as the outside work does not interfere with their schedule at the ATC.) Upon their contract completion, the inmate will immediately gain the status of a Level 3 ATC resident.
Permanent party residents can leave the facility to go to Walmart two times per month and may have the opportunity to leave on "permanent party outings" with the other PPers, as approved on a once-a-month basis. As with all movement, these outings are strictly regulated and are in no way guaranteed. Permanent party inmates can also leave the facility on a "special request" for medical and dental appointments as needed and may also be allowed to leave on clothing/shoe shopping requests once in a while (never more than once a month).
Conduct is of the utmost importance. Space at the ATCs is extremely limited and many inmates would give anything for the opportunity to be placed there. Follow the rules to the letter, get a job and keep it, and always be exactly where you are approved to be (no unauthorized movement). It is a huge privilege to be placed at an ATC and should always be treated as such. Tell your son to closely follow all of the rules and he will be home on weekends before you know it!