I've rehabbed about 10-15 Performers, and 95% of the ignitors are 'fixed' with a bit of gentle cleaning.
First: don't be rude... if a seller says their burner doesn't ignite, agree with their wise assessment, give it a half-hearted attempt, and nod while you note that will cost a bit to fix. Then reduce your offer accordingly.
Second: once you get home, carefully blow or suction out the burner tube. Most of the time that's all the fix you'll need. In other situations, you'll need to carefully remove the actual ignitor and gently clean it... maybe an emery cloth or a wire brush to clean the tip. Then put it all back together and *pop*, you're back in business.
I recently had a seller authoritatively inform me that his tank was empty and his burner was broken. I took it home and it lighted right up, plenty of fuel in the tank.