Tupac's Sex Tape Homie -- We Used to "Kick It" Like That All the Time

Don't be shocked if another Tupac sex tape pops up because the rapper who co-starred in the first one ... says he and 'Pac used to hang out like that "all the time."

Money B from Digitial Underground told a camera guy in Hollywood, he knew the tape -- shot 20 years ago -- would eventually see the light of day ... saying, "I didn't know who had it, but I knew it was out there ... so, I'm not surprised."

As TMZ first reported -- the tape shows Tupac putting his arm around his pal Money B, while Tupac is getting, umm ... oral attention from a woman.