Can I?

Have nothing to do with it or you are a party to perpetuating a fraud. Its all a part of a scam.

In most cases this is a scam that gets the sender your bank info when you try, and the check bounced and your account gets drained. There are a few real shady loan companies that send "checks" where the endorsement is a loan contract, at awfully high interest, where you can be sued, and those are poison too. Shred it. You're about to be a victim.

It sounds like you received what is called a "live check" from a finance company. (It could be a scam, but "live checks" are pretty common.) The finance company must have thought that you were credit worthy when it mailed the check to you. If you cash or deposit the check, then you are agreeing to pay the loan back with interest. There should be a Truth in Lending disclosure in the paperwork that will tell you the interest rate and other terms. As to whether not paying back this loan will get you into "serious trouble," that all depends on what you consider "serious." Not paying it back will show up on your credit report and lower your credit score. You will at least get calls, maybe letters and maybe home visits to try to get you to pay. You might get sued in small claims court. If they get a judgment, then garnishments are possible. I understand how it is to need money, but if you don't mean to pay it back from the start, it is probably a bad idea to cash the check.