I am looking to add a master suite and bathroom to a 2 bed 1 bath slab home. The existing bath is behind a wall adjacent to the space where I will add the bath. My main concern is how I tie into the drain lines. I assume I will have to chip the slab or is there a way to elevate the toilets and tie into the existing drains.

The Cheaper? Way is to raise the floor, and looks cheap?
Preferred method if looks, and not having to step up, is important, would be to chip from drain to wall, then you would see if drain runs that direction.
You may luck out and drain may exit house between this wall of the 2 baths.

Do not elevate the toilets if you ever plan to sell this home, noboby would buy it. After you jack hammer the concrete you will find the drain and come back to tell us if its ABS, PVC or cast.