May someone buy a lottery ticket on chol hamoed? If it is indeed forbidden and the person ends up winning may they benefit from the money?
It is permitted to buy a lottery ticket on Chol Ha-Moed (provided of course that this is permitted throughout the year; see here), and therefore permitted to benefit from the money.
This is certainly true where the ticket cannot be bought after Yom Tov, so that the purchase can be seen as a davar ha-aveid. Even if the purchase can be made after Yom Tov, purchasing a lottery ticket is not a classic business transaction, but rather a kind of cultural activity or pastime, and it is therefore not forbidden on Chol Ha-Moed.