According to the CAPM certification handbook page 8, you are allowed to take up to 3 times during the one year from the date of your application approval.
Yes, you will have to pay to retake your exams (see page 10 of the CAPM handbook).
Training for Project Management Professional (PMP)®, PMI Agile Certified Practitioner (PMI-ACP)®, and Certified Associate in Project Management (CAPM)®