I am looking at going to a ductless mini split system. Can you install the condenser in the garage instead of outside? These will be heatpump style that will also provide AC. I am going for a 48,000 BTU unit.

No. You NEED the airflow and volume you can't have in an enclosed space. You need that volume to draw heat from in winter and to dissipate heat into in the summer. I assume its NOT a geothermal unit with a buried loop that doesn't use the air. And even if it was... you would want it outside for noise reasons.