Old books can be profitable reading, profitable selling.
If you would like a side business that gives you great joy and produces extra income, a hobby that provides you with hours of cultural experiences or an opportunity to gain a wealth of wisdom and experiences you wouldn't find elsewhere, the rare book trade is for you. Where and how to acquire rare, old books. Local libraries often advertise sales of old books which can be acquired for 50 cents a piece or less or even free for the taking. Simply take the lot or check dates and quality. About any book from the early or pre 1900s in fair condition will eventually fetch 10 or more times what you pay for it at these prices.