As an attorney who practices in this area my advice would be to hire a local real estate attorney and ASAP have him draft AT LEAST an Offer and Acceptance to Purchase Real Estate (Contract for the Purchase of Real Estate) and it will contain the basic terms which will be followed up by perhaps,,,,,,,,,,,, an Installment Land Sale Contract,,,,,,,, perhaps with a balloon clause,,,,,, or perhaps at some time you will furnish cash in exchange for a warranty deed,,,,,,,,,,,or perhaps the owner will issue you a deed and take back a mortgage and you sign a promissory note,,,,,,,,or TEN DIFFERENT OR OTHER WAYS IT CAN TAKE PLACE...
EACH plan above has advantages and disadvantages and it depends if you're the Seller or Buyer and there are all sorts of ways this can be done THATS WHY YOU NEED TO CONSULT A LOCAL COMPETENT PROFESSIONAL EXPERIENCED ATTORNEY and dont bet the farm and take a big time gamble on whats said by anyone (including myself not knowing the circumstances) here, theres too much at stake here YOU NEED TO CONSULT WITH A PROFESSIONAL ASAP
When I represent a Seller I have no problem going with an UNRECORDED installment land sale contract with a legally permissible default clause but if I represent the Buyer Id prefer a Deed with the owner taking a mortgage and my client signing a note. Note what may be perfect for someone here may BE TOTALLY WRONG FOR YOUR PURPOSES so keep that in mind
HIRE AN ATTORNEY is my best free professional advice
John T Attorney at Law