The address in the letter and the address in the envelope differ; they're next door to each other.
I'm pretty sure they just want to buy it to rent out to people. This isn't a terrible thing, I mean there are people out there who want to rent things. But this idea that my home is little more than an "investment property" is kind of galling. When did people buy things solely becuse of present or future value, rather than buying things because they're useful or because they like them?
Why are these people collecting houses?