Udacity has around 200 courses that are completely free (but do not offer a certificate).
Udacity’s Nanodegrees (micro-credentials exclusive to Udacity) are completely paid. These Nanodegrees can be paid per month, or you can pay for several months upfront for a reduced amount. If you cancel your enrollment within 2 days of signing up, you may be eligible for a full refund.
If you cannot afford the cost, Udacity offers a limited number of scholarships for particular Nanodegrees. Here is some information about Udacity scholarships: https://www.udacity.com/scholarships
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