I can say this
On PartyPoker.com you can invite a friend and get 50 for yourself and 25 for your friend. That 75 bucks. Now, the way you can cash it out is this. Your friend needs to play 50 hands to be able to access your share and 125 to be able to access his share. So in order to get to all of the money you need to be able to pass 125 raked hands.
Well, if you go to a .25/.50 table with 9 other people then 10 hands will cost you .75 cents (provided you fold every hand). So 100 hands will cost you 7.50 and the remaining 25-30 hands will cost you a grand total of about 9-10 bucks. Since you can have multiple tables open at once then it only takes about an hour with 3 tables going.
So you can literally make the guarantee to someone that they will not lose. I have done this 9 times so far.