I started my first business at the age of 9 (1984). It was a comic books rental service. I did that during my summer vacations. My first partner was my childhood friend Amit. I got all his comics, combined them with my collection and we had our starting inventory of books. We had books including Chacha Chaudhary, Vetal, Mandrake, Archies, Pinky, Ankur, Chandan, Champak, Lotpot, Motu Patlu, et al. This needed minimal investment and I started being cash flow positive on day one since most of my cost was sunk cost as we already owned all these books.

I used the concrete space (front yard) in front of my home to setup my first shop. This whole shop was setup every day in the morning and removed in the evening.
Pricing was not that tough – we just had to be lower than our competitors (professional comic book rentals). It was 25 paisa a book per day. I also relaxed the late fee rules (just like what Blockbuster had to do after Netflix). No-late-fee was a very novel idea those days. This was critical to get our initial customer base.
We created buzz using the current viral marketing techniques. We gave one day one comic book rental free if you refer one friend as our new customer.
Customer Database was a simple notebook with columns capturing information about customers on one page and their rentals on a new page for each customer.
I used to reinvest 50% of my earnings back into the business by buying new comic book sets. One of these nights before sleeping I pledged to myself that I will invest 50% of my earnings always (even when I grow up) on books. I realize now how difficult promise that was. I still try to buy quite a lot of books but certainly not 50% of my earnings. I never understood at that time why these grown-ups always wanted to so many things in life. According to me all that you needed to survive was comics.
As an extension (a big one), I also tried to create my own comic characters. I thought about partnering with my cousin brother Avadhesh (who according to me was the best businessman I knew) for creating a new comic series. It never happened!
As I look back we used all the concepts that I eventually formally studied in my Berkeley MBA program. The basics of business remain same. The most important thing to keep in mind is to do what you are passionate about. My little comics rental business was successful because I was absolutely passionate about it. Follow your heart!
Similar with me, you reminded me of my childhood. I used to open mobile library. I had so many books (Champaks, Nandans, Paraags, Lotpots etc.) and get also from other friends and give it to kids to read and record their names in the notebook. I loved it when someone borrowed books and had the opprotunity to make an entry in the notebook.
Good Post.