Make sure you do your due diligence before purchase a domain name. You must make sure you are not infringing on a trademark. If you are, you may have your domain taken away from you under WIPO/UDRP or through court.
Check any domain before you buy, confirming there is no typo or is actually numbers instead of letters.
No refunds will be given after you make your purchase, even if you later find out there is a trademark associated with the domain.