Purchasing a building not for sale

[Jessica A.]

I've recently moved to a quaint and growing small suburban town. This town has great restaurants, shops, etc. However, it is missing a coffee shop where people can meet and gather, stop in for change of scenery for those who work from home, or grab iced coffee on a Saturday morning.

I've found this building that has been vacant for over 3 years now. One of the owners has passed, but his wife is still alive. I also recently found that they have not paid their taxes in almost 2 years.

This is one of the few small stand alone 1-story building in the downtown area (land is about 20 x 100). It also appears to have significant water damage (previously a laundromat of some sort). 

How can I go about making an offer to the widow that is fair? I've drafted a letter, but I'm unsure how to make sure I'm not overpaying for this building. Similar commercial building that is operational and leased is being sold for $375K.

Thanks in advance!