Your question is somewhat confusing. Did the letter you receive indicate that the person is wanting to purchase your home or are you a real estate agent and the letter is from a prospective client? If you could be more specific I'm sure that I can assist you as I used to work for a bankruptcy and real estate attorney and there are websites that are available wherein you can research that information.
there are people, primarily investors, who send out letters trying to buy properties at a wholesale rate, usually 10-12 percent below retail. They send these letters to people who fit a certain criteria, say those who have Notices of Default filed, or those who have lived in their home more than thirty years, looking for people that might need to sell and are looking for a quick escrow.
IMHO why would anyone want to sell at less than top price? If you need a referral to a top Realtor to analyze the offer, please let me know and I'd be happy to refer you to one.
My team and I work with many "distressed" sellers (late on mortgage, divorce, estate, etc) and would be happy to consult with you on the situation if you like. It may be something else, if so, I would agree with the other person here that you should really get an agent to represent you in the transaction to make sure you are legal and not taken advantage of.
Let me know if I can be of any help.