Direct Sales Is One of the Best Routes for Self Published Authors, and Small Presses

One of the main concerns with physical products is profit margin. You have to figure out what the cost of producing the product is. Then the retail, and wholesale value, along with the profit from each sale.
When you sell a product direct to customer, the distributor and store fees are bypassed. We're not going to speak on social media ad cost, or shipping fees because, we're going to focus on direct, hand to hand sales. So, if a book cost you $3.80 to produce. The retail value may be $15. But you sell it for $12 directly to the customer. There's a profit of $8.20 from each sales. Now, the same book sale via, an online seller, or distributor would be 50%-60% off the retail price. Therefore, you would earn $6.00-$7.50 from each book sale. The big difference in this equation is that when you make a direct, hand to hand sales you acquire them funds right then and there. Whereas, online and distributor sales come at a pay wait time of 30-180 days. Depends on the platform.
Most people think of books, and they immediately think of book stores. Whereas, when I think of books, or any product. People and demographics come to mind. I know who I write for. As an author and publisher, you should have a clear vision as to your market. From here, you can find suitable areas to prospect customers for sales. In the NYC metropolitan area, and most cities in the northeast region of the United States. Street vending is pretty much an accessible market for literature, under the First Amendment.
The thing about sales is that, as long as you can invest in inventory your hustle will pretty much determine your earning potential. As an author, or publisher. The value is in the catalog. The more books you produce. The greater the earning potential. Look at it like this. If you have 1 book, and decide you would like to earn $100,000 within a 12 month period. Each book sales at $12. You'll need to sell 8,334 copies. If you have two books. You'll need to sell 4,167 copies of each. Three books; 2,778 copies of each book. But, if you can increase the amount of sales for each book, your earnings increase. Mathematics, doesn't lie.
Speaking of books. I'm the author of several books. Also the CEO of Therone Shellman Media. My titles are available at the company website, Amazon, Books A Million, Barnes & Nobel, Google Play Books, IBooks, and Audible. 
Therone Shellman
Therone Shellman Media