Safelists and Mailers free to join
Here is a listing of safelists and mailers where I've managed to purchase lifetime upgrades. This frees up your time and is a very valuable asset so you don’t have to spend so much time clicking for mailer credits. I'd advise everyone to purchase upgrades in mailers instead of traffic exchanges because I've found them to be much more responsive for me. The traffic exchange upgrades keeps you from having to click for credits and keeps your ads in rotation, but your mailer credits are much more specific and more responsive.
I cannot stress enough the importance of using your mailers DAILY! After all, it's a numbers game so the more mails you send out the more money it can bring in for you. I've made cash from winning prizes surfing, but I've made much more by sending out my opportunities through mailers than through surfing. So, if you aren't using mailers already, you are losing money by not doing so. Get started by signing up to these mailers and upgrading where you can so you don't have to click for so many credits. These mailers all have (or had) a very inexpensive Lifetime OTO most for $10 or less and always be on the lookout for new mailers with great OTOs.
Here are some classified ad sites or text ad exchanges. Watch for some great steals as you log into the sites, I've found some really great deals!