35. If someone is given money to buy something specific, e.g. a washing machine, a new coat, etc., the recipient of the money becomes a shliach to buy the item for the one who gave him the money, even if he is the one benefiting. Therefore, he does not need to take maaser off that money (חזו''א, דרך אמונה פ''ז ציון הלכה סקס''ז ).
36. If he received more than he spent to buy the item, e.g., he received 1,000 shekalim to buy a coat but the coat only costed 800 shekalim, he must take maaser off the entire amount he received. This is because he is clearly not a shliach to buy the coat; rather, he was given money to buy it himself, and maaser must be given for that money (הגר''נ קרליץ, באורח צדקה פ''ט הער ה מ' ). This is true even in a case where he has to pay some of his own money to arrive at the maaser.
