The 35%/65% split is for an Incognito funded stake on the Node. When someone buys a Node, it will come pre-staked with 1750 PRV. Even though this 1750 PRV comes loaded on your Node, you do not own it. Incognito is providing the stake to lower the technical barrier to entry for the Incognito system. For the convenience of this funded stake, your earnings are automatically split 35% to you and 65% back to the funded staking pool. This funded stake is not a loan, nor rented, therefore there is no payback. The earnings split will remain in effect as long as you have the funded stake on the Node.
If you would like to keep 100% of the earnings, you will need to unstake the Node. The 1750 funded stake is returned to the funded staking pool. Once unstaked, you would then privately stake with 1750 PRV. You can buy the needed PRV on the pDEX, or use your PRV earnings or even a combination of both. However you will need to provide the full stake of 1750 PRV, no matter where you source the PRV. You cannot stake less (or more) than 1750 PRV on a Node.
Once you’ve privately staked the Node, you will keep 100% of the earnings and will no longer split the earnings.