So I have been reading the rules, and unless there is something I missed, which is possible, my rogue could have a Bulette (Creature 8) as a mount at level 2.
At level 2 Rogue, I raise Nature to expert and take the Bonded Animal feat. Then all I need to do is roll a DC 20 Nature check during downtime and bam, the animal is permanently helpful to me. And if I have the Ride feat, then I don't even need to roll a check to get it to stride for me.
Also with it being helpful to me, I only need to hit a DC 14 to get it to do an action for me.
The Base DC is the Will DC which is 24 - Will Save (+14) + 10. However the if the animal is helpful to me, which it is, then it increases my degree of success by one step, which means a failure becomes a success and I just need to get over a critical failure, so 24-10=14!
Also with Assurance (Nature), then I can't fail.
I am trying to see if I am missing anything in the rules as written.