Here is a link

http://www.lbah.com/Feline/fiv.htm

The things I would mention....

Feline FIV is different to Human Aids and inter-species infection CAN NOT occur.

FIV cats MUST be housed inside at all times, as they risk infecting other cats if allowed to roam.

FIV cats MUST be homed on their own or with other FIV positive cats.

Although they can cost more in terms of medical care towards the end of their illness, they still need love and will reward the new owner with years of love. (NB.Would your shelter help with this cost ?)

I am not sure on FIV cats longevity issues.