- Do a search for similar names.
- Check with the Secretary of States office in the state you want to register in for business registrations.
- Check the federal copyright and trademark database for similar registrations.
Regarding different but similar spellings. It may not be worth the trouble you can encounter if the owner of the name you copy wants to vigorously enforce his tradename. The legal fees will eat you up to try and defend yourself. Avoid using similar type fonts, colors, and any designs the original trademark may use.
Companies spend a lot of money on marketing and advertising and want to protect their investment. Your product may be different now but the company may have new products under development similar to yours . Also, many companies want to avoid any confusion your name may cause, especially if the company holding the tradename feels your product or service may harm their reputation.
I am not a lawyer so please consult an attorney in your jurisdiction for proper advice. My advice is only given from the standpoint of my own experiences with start-ups and advice given by my attorneys. They do know best. You can pay them now, or you can pay them later. It’s all up to you.