Don't forget to factor in maintenance costs. If you own the place, you're on the hook for maintenance, which can be pretty high for old buildings. While the asset may appreciate in value over time, the cost of carry may negate that price appreciation.

Or you can decide not to do maintenance but then the value won't appreciate.

I guess it's a nice place and people want to have events at nice places and if they held it for 200 years it would be a good investment?

One thing your numbers probably don't consider is the cost of hosting the guests? For a wedding that is usually not considered the responsibility of the hosts, but it is still a cost associated of the event. In this case, one of the reasons why this building seems to be a good fit for the project is that most of it has been carved up into small bedrooms. (I think this happened in the early 20th century when it was used as student housing, if I remember what Owen told me correctly.)