When you sell the property you will only be entitled to offset a pro-rata portion of the capital gain (for which you were primarily resident) against the primary residence exclusion of Rm2.
The rest will be subject to normal CGT.
The rentals will be subject to tax as usual, and then you will be allowed to set off relevant expenses against that income.
So long as it is rented to a 3rd party, and not a connected person, I dont imagine you will have a problem with it being ring fenced/