Don't use a 50/50 sale when you dont have to. Get your money up front. This reduces the potential problem of incomplete payment. If your buyer cant pay more than 50% down this may be indicative of a problematic financial situation.
In buying and selling over the years and in liquidating estates I have always paid the full price up front or collected the full price up front even with dealers. Asking for full payment is a good way to weed out questionable buyers. Life is too short to deal with flakey potential buyers. There are plenty of strong buyers out there who are able to send you a cashiers check by overnight mail.
Always check out your buyer. Consider and provide for the possibilty that your buyer won't qualify as a lawful transferee. This has been an increasing but unusual problem in recent years in my law practice.