I agree with the others, if you are getting a rescue horse, I would suggest you first work on trust and get to know the horse. Then I think it's best to spend at least six months purely on flatwork. If he/she is younger, then even longer.
Once you have gotten that straight, then start slowly with small cross poles, and abit of grid work, and progress upwards.
For the jumping, I highly recommend getting a trainer to help you. Or even an instructer.
Let us know about the horse hunting.