Concrete in drain of a foreclosure - how do you avoid and/or fix? What other problems have you encountered?

[Andy Hayes]

I haven't made a purchase yet but plan on buying distressed homes and fix them up for rentals.
One nightmare that's kept me awake is the idea that the person foreclosed on has poured concrete down the shower/toilet/any other drain.
1) How do you check for this? I'm thinking that I'd want to bring in 5 gal water jugs and pour the water down various drains in the house.
... since most foreclosures I'd be looking at would have water shut off, I don't see any other solution to check for this.
2) If you purchase a house with concrete poured down a drain and the concrete has made it past the J bend in the trap, I assume you've got no choice but to tear out the pipes all the way until the pipes are free of concrete. I assume this means tearing up the concrete floor to make that happen. ... and I further assume this is pretty darned expensive.

3) Is it pretty easy to spot if the copper wiring has been removed from the house? While not desirable, I assume this is easier to work with than major plumbing issues.

4) Any other major pitfalls to watch out for?