Sorry if I'm not clear, "free" in the sense for rebate cards offering > 2.6% rebates. Especially for payments that do not take credit cards and you'd have to pay for it anyway.
Anyway, this is a miles card and not a rebate card. If you're looking for rebates, then this is the wrong card for you. For a miles card, most people on this forum are fine paying for Citibank PM annual fee, $192.60 for 10k miles, which works out to $0.01926 per mile. So paying extra 2.6% for 2.4mpd works out to $0.010542 per mile, which works out better than the annual fee option.
As per above. Buying miles is fine, as long as the rate is sufficiently low, plus this doesn't consume much of your time. I've used to do mileage runs, which involves buying dirt cheap air tickets that gives miles, then actually flying the flight to get status miles plus redeemable miles, but changes to the program have deemed this not that feasible anymore. With double qualification miles promo, I can be gone (and flying) for one weekend and gain 30 to 40k elite qualification miles as well as redeemable miles.