If you don't like living in a converted garage, you can move.

If you don't believe that the converted garage is up to code, or is a lawful apartment, you can complain with local housing authorities. If required to move as a result you may have remedies against the landlord.

If your landlord shuts of the power or otherwise tries to unlawfully evict you, you can commence a lawsuit against him asking that he stop taking unlawful actions and for appropriate compensation.