My advice would be...yes create your own ads.

Put some together...people want to see your style. You can use current products or make up your own.

A little tip: Go through your local newspaper and look at the local ads. Most suck and have no direct response methods to them. As a copywriter you can look at them and know how to change them to skyrocket the response rates.

Also, once you've rewritten the local ad...you can approach the business and show them the new ad and work out a deal with them...you don't have to have a portfolio to show because all they will care about is the ad you've written for them. It's a great way to get your business off the ground and make some good money at the same time.

Edit: Although I talked about ads in newspapers, you can do the same with sales letters. You can create your own for products and have them to show.

Guess I read the title and immediately thought about display ads.

Thank you for your input max5ty. I'll go make some samples then.

Samples are absolutely crucial! Whenever you apply for a gig make sure that all your materials and cover letter are flawless. We receive so many applications from writers who make tiny, unnecessary mistakes. Those mistakes make you look unprofessional and sloppy.

Yes I have had great success with simple adds. Its all about placement of them thought.

Hey, Wytnyt -

I guess I can't post links until my post count is higher, but there was a really good article on creating spec ad's to be used as samples in your portfolio. Just google "spec ads about.com" and you'll find it I'm sure. Useful information.