Evaluate your reasons for seeking this type of fiancing as well as the reasons why a seller would want to carry financing in lieu of receiving cash from a bank at closing.
Reasons a seller will do this include: He/she needs to in order to sell the property because it is not moving on the market or it is difficult to obtain traditional financing. Or, because the seller personally knows and trusts the buyer. Or, because the seller views this as an investment. A seller looking for investment return will srutinize your credit and qualfiications, perhaps more so than a bank.
Buyers may seek this because they look for a deal when purchasing a property that a seller has not moved and strike a deal. Or, the property may be one that is difficult to obtain financing. Or, the buyer may have diffficutly obtaining financing.
Understand an owner's motives for their willlingness to carry paper and make sure it works for you. If you are looking for prospective owners to carry paper, look in the direction that best suits your need. i.e. If you are willing to undertake a challenging property, start looking at those and inquiring if those sellers would consider financing.... more