You have to spend money to make money. Why not make money while you spend. I have many business expenses such as paying for shipping at the post office , Ebay and Paypal fees, and buying items to resell. I try to always pay with a credit card that has cash back points. These are also lots of cards that offer sign up bonuses. I have recently used 5 or 6 different credit cards that have offers such as :
spend $500 in 3 months and get $200 cash back
Spend $2500 in 3 months and get a $500 Walmart gift card
Spend $3000 in 3 months and get $500 cash back
Get $100 cash back after your first credit card purchase
Get $50 cash back after your first credit card purchase
I use these cards long enough to get the bonus then I change to another and another and another..... I make over $1000 a year extra using this method!
There are lots of these available - see the following links