I am going to invest in a friend's startup company in the fashion industry in exchange for X% of equity. Is there any tax write-off for minority investors?
As far as I know, you will have no deduction simply for investing in the company, however, should it lose money you may be able to claim the loss at a greater rate than traditional cap losses- these are $3,000 per year. Qualified small business stock investments are able to deduct up to $50K/$100K (single/married) against
ordinary income. This can be valuable in the event that things don't go as planned.
In terms of write offs - in deal like this they will likely go to the business, because the expenses that are incurred are reported by them, not you.