Easiest and cheapest way to earn Bitcoin by doing some mirco jobs, PTC sites and Faucet. It is time consuming but it actually pay Bitcoin. This means that you will be basically be doing small task and fractions of coins for the time you spend. Well known micro earnings sites are Bictoin Faucets. PTC websites are actually sub-category of Faucets. PTC websites will usually have you click on an ad or on button on the site in order to make money form ad sales. In return you will get a small amounts of coins.
Micro earnings take a lot of effort, yield very low income but are usually a very safe bet.