I agree with the posters...have a plan B if boundaries are crossed.
It's wonderful that your sister went to rehab and completed the program. It's equally wonderful that you are going to assist her in getting back into the world.
However, this world, as we all know have many temptations and that is where "working the program" comes in. If she is serious about her recovery you will see it. If you begin to see her doing questionable things...then her recovery is lapsing.
Sober living is a great and often cheap option for those getting out of rehab. I would highly recommend it it as she can live with sober people and still be apart of your life.