In the OP the person involved might pay $1400 USD per month to rent a vehicle. Unless you are travelling long distances much of the time, you can take a lot of taxi rides for $1400. Practically speaking a car spends a lot of time sitting in a driveway going nowhere. Expensive is subjective. Buying a car for a stay of a few months sounds like lunacy and a really poor financial decision.
Between the two option that was present in the OP, renting for $1400 USD/month or buying, the lest poor financial decision would be to rent. A car is not being depreciated $1400 USD/month here. Let's say that the person might stay here for 3-4 months. That person might purchase a car for let's say $20k and would have to pay the 2% tax and something more, so let's say around $500. But when they're going to leave the car would most likely still be worth $20K, so the only thing that it would have cost would have been the $500 and the insurance cost...
So it all depends if the person doesn't mind doing the paperwork and everything.
As I stated in one of my posts, a friend of mine, does that EVERY time he comes here, although he never buys a "new" car, but something reasonably used, and many times he's even able to make a profit out of it.
And as I guess this person would be staying in the capital, so then it doesn't really make sense to rent or buy, just use taxis, uber and whatever other transport that is available.