Land Contract or Mortgage Assumption

[Jeff Gebhart]

Friend of mine always told me buy on a Land Contract never sell on one.  Probably good advice.  We have never done either but may have the opportunity.

Can someone help me with these questions.

If we buy a property on a LC, what happens when the seller defaults on their mortgage?  I assume our payments go directly to the seller and they make their payments from that (if not then than my worries are irrelevant).  I am worried that a seller that is in default has a pattern of poor money management and that won't change.  

How does a Mortgage Assumption work?  What are advantages/disadvantages?  

Any advice would be greatly appreciated!