For anyone contemplating this hobby, but not sure you can do it without getting a lot of cards - it is doable on a small scale. Yes, taking advantage of SUBs and churning is very lucrative. I have said it here before that I am in awe of the people who can do that; I don't have it in me. That being said, with my 6 cards that I do not churn I was able to:
-book SW flights for a summer DW trip - 4 round trip tickets - only OOP was the $5.60 each fee. I could cover this with my Discover IT cash back if I wanted; but I won't.
-buy 3 Park Hopper/Water park tix for 8 days using MRs, URs and a few other minor reward things - no OOP. (4th park hopper was bought by the friend who will be traveling with us)
-have DVC so no OOP there except my dues (which I sometimes cover with rewards).
-will get Disney GC using MRs and URs from now until the trip to hopefully have no (or very little) OOP food and expenses while at DW. Also currently taking advantage of 5x rewards on the Chase Disney card that rarely use.
So if I can pull off getting enough Disney GCs with my CC rewards this 8 day vacation will cost me $44.80 (and DVC dues which I pay whether I go on vacation or not). I currently have enough MRs and URs to cover all meals and have some extra spending money.
So if you think you can't get a free or an almost free vacation without serious churning, think again. Careful planning and careful use of CC rewards makes it possible. I put just about all household expenses that don't require converting MOs, etc or cost me more money to use CC on my 6 cards.
Disclaimer: you need to always pay your CC bills in full or this hobby is not worth it. I pay them weekly - sometimes more than weekly.
ETA: the only annual fee card I have is the CSP ($95) and I pay that fee with my Discover IT cash back. So no AFs for me either. And I won’t do business cards.
ETA2: If once you find that you can do this on a small scale, you can try churning or expand your card collection at your comfort level. I do very occasionally add or replace a card. Most recently I swapped my CF for the CFF and got P2 the CFU.