Our company buys and sells used equipment.  I need to make a form on our site that visitors can use to submit information about equipment they are willing to sell to us. 
This would include simple info like make, model, and brief description or asking price.  We'd also want to capture the visitor's information, name, phone, email, etc.
What would be the best practice for implementing a form like this?  Custom Record?  Online form?  As someone could have either one of several submissions, it would be great to have the form expandable into more lines if the visitor needs them.