Can my mom cash it out for me? Does it have to be under her name?
No, banks will not cash any check. if she can take the check to a branch of the issuing bank she should be able to cash it there but banks generally will not cash a check when they have no relationship with the person writing or cashing the check.. Most stores and many banks no longer take 3rd party checks so endorsing it over to her mom could still be problematic. Government and payroll checks can usually be cashed for a fee at Walmarts or cash checking businesses but personal checks can be difficult to cash under these circumstances because nobody wants to take a chance on it.
All you have to do is endorse it. Sign the back of it and you can cash it at any bank - with or without an account - or at any store that takes cheques. You might need to cash it out, yourself, though as they may ask for identification. Usually, if it's endorsed, banks will cash it out even for your mother.
1.) You or your Mom will have to have an account - and they will hold the funds until it clears, or
2.) You and your Mom take it to a branch of the bank that issued the check, or
3.) Check cashing businesses will cash it for a fee.
You can go to any bank and pretty close to any store, they'll cash it for you, but right your name on the line on the back of the check first.
What if it's a check from a website where I sell things. Does that still apply?
Well, I guess things work differently over there.
You're just signing your name on the back of it.
What are you doing by endorsing it?