creative financing help with poor credit

An older family friend is selling her house and is willing to let us buy using a short term land contract and us going to a conventional mortgage in 5 years. We have horrible credit (a recient credit card bankruptcy) and will have no down payment. Does this sound like a good option? Is a downpayment necessary for a land contract in all cases, or is this something that varies depending on the seller? Also, who determines the amount of the land contract payment? We will probably be using a real estate lawyer to do the paperwork. Any help will be appreciated!