Way to earn a lot of money with small invest

1) Bought an old bike for 10 thousand and after spending 

10 thousand on it, polished it and sold it

 for 30 thousand, 10 thousand profit.

2) Bought an old auto for 1 lakh rupees and

 put it on rent, money will come every month

There are many other ways by which people are earning a lot of money.