Website giveaway -- No purchase necessary - any problems in doing this?

To promote a website -- I was planning on giving away a (used/vintage) HP calculator just for making an account



there would be NO purchase needed OR shipping charges and would be worldwide offer -- it would be like ';free to the XXX person to sign up '; (this is an ecommerence website that requires a log-in)



there will be NO spam emailed after the drawing etc .I use PayPal so I am not collecting C/C numbers etc



Am I getting into an area that may be more problems / hassle than its worth ?