sewer inspection?

How many of you guys have had sewer scope inspection prior to home purchase?  If a house had a history of tree root issues requiring removal of tree because of damage to nearby walls, would this be something you would consider?  If a problem was found, would this be something to discuss with seller for repairs or credits?  Also do you need to get special permission from the owner to do a sewer scope? 

TIA

We had one done while in escrow to purchase an older house.  The scope cost around $200 and the entire street had 60 old trees in front of every single house that were city owned/maintained and densely rooted.  The scope was more to ensure that the pipes from the cleanout onwards to the sewers were not obstructed, but shortly after closing escrow the house got backed up because the previous owner's child flushed a fabric napkin into the toilets (the scope wasn't any help there because the clog that resulted was before the cleanout section of the pipes).  Ended up costing $500 to get it snaked because it happened during Easter weekend. 

Moral of the story is do the scope (we didn't need sellers' permission) but don't expect that it will exempt you from all the unforseen headaches and costs of owning your potential property.  I will say this - after having owned a home with a 30 foot tree out front, roots may the least of your worries - we had 10-15 foot tree limbs fall and damage our cars in the driveway and out front 3 times, so I'd be more wary of what's above than below.  YMMV.

Related story from a friend in LA County:  Their sewer backed up due to tree roots.  He had resigned himself to a very costly repair bill, but luckily got ahold of the right person in the city before having the pipe dug up and opened.  The city had their inspector on site when the pipe was broken open to verify the roots were from city-owned trees.  Therefore the city coughed up the $$$ to fix the problem, to the tune of over $40k, since it involved street closure and breaking into the asphalt and re-paving.  Had a city inspector not been present, my friend would have had to eat the cost.