You can tweet and earn money through Twitter advertising. It's called 'Sponsored tweets' or 'promoted tweets' when an advertiser pays a 'tweeter' to tweet products and services.
How many Twitter followers do you need to start selling tweets?
Services that allow you to sell tweets have minimum requirements, on how many Twitter followers you have, before you can create an account. I've seen a BuySellAds.com tweeter selling tweets with only 1754 Twitter followers.
Most advertisers buy tweets in bulk ~20,000+. You'll sell more tweets the more followers you have.
How can I sell tweets?
There are online service out there you can use to create an account with that will set you up with advertisers. Below is a list of 'sponsored tweet' or 'promoted tweet' services along with their PR(Page Rank).
- http://buysellads.com/ pr 6
- http://sponsoredtweets.com/ pr4
- http://pay4tweet.com/sell.php pr3
- http://www.seoclerks.com/sponsoredtweets pr3
It's important that you generate Twitter followers of a certain demographic. You can generate followers by following others. Use Twitter's search option to find and add Twitter followers of a certain type, and many of them will add you back. Trouble shoot adding twitter followers.
How much does it cost to buy tweets?
The cost varies widely between services and demographics. I estimate it to be about $1 = 50-400 Tweets.
Twitters official explanations and guidelines on promoted tweets.