How does a land contract work?

[Jack Slattery]

A couple want to sell me their home on land contract.  Here are the details:

1 They owe $52,000 with a payment of $409 P&I, tax & insurance.

2  The bank won't let me assume the mortgage because I am an investor.

3. I am willing to pay $55,000.  I will pay them $3,000.  

My question is: What happens now?  What do I need to do to keep me and the seller safe

And the bank happy.