Submitting a Offer- W/out a Realtor

[Kane Griffin]

Hello all, 

I found a property in Texas City, TX that has a potential for great cash flow once it is rehabbed. They are asking $120,000, which I personally think is to high after evaluating the comps and considering how outdated everything is. This property will need a full rehab from top down, it still has all of the original finishes from the 70s. I am planning on offering 90k which is low for the property but it gives room for a reasonable counter offer. I must add that the seller is motivated to sell. I plan on writing this offer letter myself and would like to get opinions from the professionals here on BP. What are the key components to this letter that I must include to save myself legal issues and money as well as making it look professional?