themoneyconverter.com/USD/MUR.aspx
I would recommend not moving to port louis, but close to port louis. To be honest, port louis is just a business center and very few people actually live in the city
The cost of a 3 bedroom house would be much less if your are just 15 minutes away in either direction. WIth this life would be much easier.
Secondly, the cost will vary depending on how lucky you are at the time. You can find something perfect with a garden with a price ranging from 20,000 - 30,000 rupees. Anything less, you will just have to be very very lucky.
To search I would recommend checking out the website l'expressproperty.com to get a head start on looking.
I would say that with a family of 4 you will need minimum 80,000-100,000 rupees a month to live. You can take a look at themoneyconverter.com/USD/MUR.aspx to convert.
Take care and good luck