If you select the one-time payment option, YES! You will have to pay just one time, and you will get access to the course and all materials forever.
If you select the three monthly payments option, you will be billed the first payment at the moment of the purchase. The second payment will be billed 30 days after, the third and final after 60 days of the initial purchase.
In both cases, you will receive full access to the course immediately.