Send them a letter telling them you found their house to be apparently vacant.

I buy stuff like this all the time in my area, so you must have someone in your area that's doing the same, and all you need to do is write them a letter.

Learn all you can with getting lists and sending postcards, letters or whatever so that they will call you.

If they currently rent, get a letter from the landlord.

Another thing to consider doing is to get your financing figured out and have that lender give you a loan letter that says their average time it should take them to close a loan and the maximum amount you qualified for.  

Today's little letter was a sales reply not a question.  

How do you go about sending an offer letter to a seller's agent if I am not represented by a buyer's agent?  

There are many more issues in addition to ones mentioned above & they would not provide me any proof or evidence even after emails & letters.

That should keep your personal things out of reach if your business has any legal problems.Another thing you might consider doing is to get any financing figured out and get a loan letter from your lender that states their average loan closing time and the maximum amount you qualified for.  

Well several months down the line I get letter saying property has defaulted and to be auctioned off, property was auctioned off but sale was reversed because owner filed chapter 13.