Serious answers only.
Suggestion:
Sure it could backfire. There is the possibility that six months from now the car could need unforeseen repairs, your income could go away or be reduced, you or a dependent could get sick.
Do you need a car right now? If not, and this would stretch you at all, then you have to think long and hard about the risk.
Do you have any other accounts at all? If so, making your payments on them like clockwork will slowly build your credit rating, and you could be saving the money that you would otherwise be using for car payments.
I am 65 years old, and with one exception I have never bought a car on credit (paid that one off in under a year). Unless you live in a city with good public transit to get you to work (or school, or whatever is important in your life right now), don't put yourself in a situation where the repo man can drive off with your car in the dead of night because you were late on a payment. That's too big a risk to take. Not to mention such events would make your credit score worse, not better.
If you don't have a car and absolutely must have one; if your income is guaranteed for the next 18 months; if you have health insurance, then maybe this is a good idea. Otherwise keep in mind there is risk along with the possible reward.
Good luck.

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You can use this credit monitoring service to pre-estimate future scores for different scenarios of such payments – buildcredit.ifastnet.com
If you can handle the payments, go for it. Just be completely aware of what you are walking into.