Edit (12-12-17) : I have found a partner, but if you are willing to join, we're open!

I will be peak-bagging in Chile and Argentina from mid-January to late-February. Objectives are first Marmolejo and San José, then Ojos del Salado and Llullaillaco, then Mercedario and Aconcagua.
I chose non technical routes since I planned on going solo, but I am comfortable on alpine PD and basic glacier travel if we are a team.

Even if you don't want/need a partner to climb with, I will be more than happy to share some of the transportation costs if you are also heading for one of these mountains.

I am from Canada, and speak English, French, basic Spanish and basic Chinese.

Anyone has tips on renting a car in Copiapo to drive to Ojos del Salado, and hitchhiking from Barreal to Mercedario?
And which permit you have to get for Aconcagua if you go in by the Horcones valley and out by the Vacas valley?

Anyone has tips on renting a car in Copiapo to drive to Ojos del Salado

It's probably better just to hire a driver rather than to rent a car and let it sit there. The roads are really rough and rental cars that are capable of reaching the trailheads tend to be very expensive.

For what it's worth, I thought Ojos was the least attractive and least fun of the peaks I have climbed or attempted in the Andes. In my opinion at least, there are other mountains in South America to attempt that are better.

Thanks for the info. I thought since I will already be acclimatized that I could check weather from town and rent a car for only a few days to bag the peak alpine style, instead of the 1000 USD transport I got quoted that would definitely put me off that mountain.