Rabbi Avrohom Baruch Zachariash teaches the halachas of Chol Hamoed with the Mishnah Berurah (O.C. 539).
0:30 Doing business on Chol Hamoed; Having a gentile doing business for you.
03:30 Collecting money for farmers during Shemita.
08:25 Buying shirts at a Fashion Show during Chol Hamoed
11:46 Permitted to take advantage of profit but some of the money must be used for Simchas Yom Tov.
15:25 What is considered a “big profit”?
19:17 Why does some of the money need to go to Simchas Yom Tov?
26:05 Sif “Beis” collecting loans. When does a business deal turn into a loan?
34:30 Writing on Chol Hamoed