I wish I could give you a more straightforward answer
but I
unfortunately can’t. As you already know, there is no such thing as a free lunch
(or is
there?) so you will have to work really hard to get an opportunity like that. As
usual, it
is easier to get discounted prices on your travel cost, like, a free night stay
in a hotel
or a free tour in the city you visit. If you’re trying to follow that path.