Purchasers rarely walk away from substantial down payments. Most seller-financed transactions that I broker are between 25 and 50% down. I do not recommend a seller take less than 25% down. A well-written sales agreement laying out the terms of a note and security agreement are a must. These actual agreements should be prepared by an attorney and recorded in the public record with a list of all assets conveying as collateral in the sale. The vast majority of owner financed transactions I have put together have worked just fine. However, in the event the purchaser refuses to pay and will not voluntarily turn over the business and its assets, the seller must foreclose through the courts. If you want an absolute guarantee - get all cash. This will, however, somewhat limit the number of potential purchasers who could buy your business unless it meets the qualifications for an SBA or other commercial loan or you find someone willing and able to pay all cash.