People who are looking to buy are looking to set down roots, maybe have a family - in short, they're probably looking to stay a while and will want to have a lot of bases covered right off the bat (whereas renters may be thinking they will move or buy elsewhere 'when the time comes' whatever the 'time' might be).

What makes that scenario much less likely to happen today are the reluctance of the banks and lenders to leverage themselves that much, the forcing, by regulation, to prevent them from getting too leveraged, and the collapse of those toxic assets that used to be traded around like a game of musical chairs, with the value only set by whoever was dumb enough to pay it, in the hopes there would be a bigger fool down the road. 

I know both you guys try hard to prevent this from happening. 

In other words, I do not think adding a co-signer really prevents a bad tenant from proving to be just that...

My advice for newbies is always to do as much research as you can (and @Casey Miles made a GREAT point about being aggressively patient) but to take the time to ask yourself (and your family) and few important questions to help weed out options and prevent analysis paralysis.

You don't want obstructions, but the trap will prevent any nasty sewer smells from coming up the sink.

I am a big fan of preventive measures, but is this something I should really jump on right away?

Real estate is a tough go rooted in death.

Whether working as an agent or not, there is nothing preventing anyone for bringing suit making allegations.

But we often buy houses that have been sitting empty for some time and have plumbing lines that have become blocked with tree roots and debris.