The old tradeline company is looking for more cards.
After still more research, they are still only one of two companies that I'd recommend (and currently the main one I'd recommend, since the "new" company, as we've been calling it, has a huge glut of cards).
Criteria: Barclays, Capital One, Citibank, Discover, PNC, US Bank, USAA. Minimum $5k limit, minimum five years old. They will take cards that are younger if they have a very high limit, or cards that have a low limit, if they're very old. Doesn't hurt to ask on a particular card, but if it's newer and with a low-ish limit, it probably isn't useful for selling tradelines.
They obviously pay more for higher limits. Card age has no effect on payments with this company.
Here is their commission schedule:
Discover, Citibank, Barclays, US Bank, and PNC - 2 Month Cycle Commission:
Limit $5,000 - $15,000 and 2+ years old - $75 per spot
Limit $15,000 - $20,000 and 2+ years old - $125 per spot
Limit $20,001 - $30,000 and 2+ years old - $175 per spot
Limit $30,001 - $40,000 and 2+ years old - $200 per spot
Limit $40,001 - or more 2+ years old - $225 per spot
Capital One and USAA - 3 Month Cycle Commission:
Limit $5,000 - $15,000 and 2+ years old - $75 per spot
Limit $15,000 - $20,000 and 2+ years old - $150 per spot
Limit $20,001 - $30,000 and 2+ years old - $200 per spot
Limit $30,001 - $40,000 and 2+ years old - $250 per spot
Limit $40,001 - or more 5+ years old - $275 per spot
2/3 month cycle means you are paid that one amount to keep the AU on for 2 months or 3 months, respectively.
Disclaimer: I will get a referral commission when you sell AU spots, but you will get paid the same whether you use my referral or not--it will not reduce your payment to have me as the referral, and for this month, you'll make $150 more than you would otherwise due to the signup bonus.