I dunno if you're intention is to buy a used or a new car but most of them are more expensive due to high importation taxes and associated costs.
Depending on how much you want to spend and whether you're opting for a reconditioned vehicle, you might find that you will be limited to Japanese makes - which there is a high market for.
An example is a 2001 Toyota Corolla selling at Rs200,000 which is around 4 grand. You'll find the same model in UK at around half or less.
If you want realistic costs of some car models, you can check on the Lexpress newspaper website.
It is a beta website at the moment and all listings are in French though but you'll still be able to hover on some prices bearing in mind the exchange rate at the moment is around £1-Rs51.
I would not personally go for a reconditioned Japanese car (so easy for them to reset the counters digital or analog and preset at a realistic mileage).
I would buy a 2nd hand vehicle off someone who's bought it from new with all documents and Full Service History.
Hope this makes sense. There's a few car dealers with websites (hopefully with an updated list of their cars) if you look at the Mauritius Yellow Pages.