Yes, you will need permits to climb both Kilimanjaro and Aconcagua. You must also hire a guide and at least one porter to climb Kilimanjaro (or at least it still did when I was there). A climbing permit is also required for Aconcagua. I haven’t gone to Kili in too long to remark on permit rates, but I have been to Aconcagua numerous times recently and can speak to prices. The low season (November 15 to November 30 and February 21 to March 15) costs $582. The fee is $800 if you climb during peak season (December 15 to January 31). Trying to go around the permission system is not a good idea. There used to be tales on Kili that anyone caught climbing without a permit was discovered dead or disappeared.