I dunno, actually... I feel that you can't put a price on one's soul, but what does 'Death's Slave' mean?
Twisted Metal 2 Grimm sorta thing? Where you gotta walk around and collect souls for him? That would suck.
If the opposite is true, where you don't give your soul and you go to Heaven, I'd probably not take the deal. If there is no certain life after death, other than this deal, then I would have more trouble deciding. Dying and disappearing into oblivion, where consciousness just fades to nothing doesn't sound fun. Its fun to think about, but not experience. If you play a 'good' kind of evil slave for Death, perhaps. Helping to guide them to their better places would be amazing... However, a 'bad' kind of slave for Death would probably play with my sanity.