You should never sign a contract of such significance without consulting an attorney. Seek out volunteer lawyer services at bar associations, courthouse libraries, law schools, etc. for a pro bono attorney that will take a look at the contract for you.
You could begin searching for help with the following agencies:
New Mexico Legal Aid
200 E. 4th
P.O. Box 1087
Roswell, NM 88202-1087
Southern New Mexico Legal Services
300 N Downtown Mall
Las Cruces, NM 88001-1247
You are protected through the end of your lease. Lease with Option to Buy contracts are very technical and you do not want to sign an agreement of this nature without advice of counsel, regardless of what you've read on the Internet.
Please note that I am answering this question as a service through Avvo but not as your attorney and no attorney-client relationship is established by this posting. An attorney-client relationship can only be established through signing a Fee Agreement and paying the necessary advanced fees.