Can I forclose on a purchaser for non-payment without going through the legal system?

The short answer is if the "purchaser" refuses to voluntarily return the property to you you'll need to use the legal system to foreclose or evict depending upon how you structured the sale of the home. This issue will be very dependant upon the facts of the case.  I recommend that you consult with an attorney on how regain possession of the property. Good Luck, Don Eby