We've made an offer on a house on a concrete slab down in Florida.
We've always owned houses with a crawl space. We want to move
around a few walls and make two bedrooms into one and make the
bathroom bigger. Also, we need to add some drains in the kitchen
for a sink in a different location.

I was a carpenter for many years, so I can deal with any issues
involved in shifting interior walls and their impact on loadbearing,
and I understand that I can get a concrete saw and carve in a new
drain, but how do I avoid plumbing that is already laid in the floor?
Do I need to get a detailed layout of where everything is in the
floor? If this doesn't exist, what do I do?

Thank you, Michael