Dear OP,
There are no circumstances where it is remotely acceptable to hire somebody else to take an exam on your behalf and by doing so, you are in-effect committing fraud. If your post is genuine, contact your tutor or course administrators and have a discussion about your personal circumstances as soon as you can.
I have been involved in investigating a number of academic practice offences at my institution over the years and I can assure you, the likelihood and consequences of getting caught are much higher than you might realise. Typical punishments for those found guilty (which for us is based upon 'balance of probability' and not upon 'beyond all reasonable doubt') range from complete failure of the module all the way up to dismissal without academic credit - Only last month an international student was dismissed with nothing after completing nearly 3 years of his degree programme and in the process lost his right to remain in the country. For some students, being found guilty may also mean a complete prohibition from membership of certain practice-related professional bodies - in some instances for life.
I have fairly recently investigated a number of examples of students who have utilised 'essay mills' (now illegal in the UK) to produce work on their behalf and in most instances, it is pretty obvious. Whenever there is doubt, we reserve the right to conduct a viva voce with the student to determine if their knowledge in-person matches what their written content and will also compare their submitted work to previously submitted examples, a process that bring further scrutiny on the student and sometimes even provides evidence of previous wrongdoing.
In a number of instances, students who utilised 'essay mills' or used 'ringers' have been subsequently blackmailed and were forced to pay cash to avoid the 'essay mill' from informing the university. Indeed two examples I investigated were tip offs from 'essay mills' whose clients had not paid them to keep quiet afterwards!
Just don't do it...
R