I figured out the cost to build an inn, roughly 700gp using the readily available forest to pull lumber from. Then I figured out a rough idea of how many rooms with would have (10), how many would be utilized on a daily basis (3 on average), what the resulting annual total that would result in. 1,095gp. Having been involved professionally in the purchase of a company, I decided to use a little of that knowledge here. To determine the selling price of a business, my CEO used a process of adding existing capital (ie the value of the stock in the warehouse, in this case I used the 700gp cost to build the place) and the average sales total for the year, he used 1.5 times. (I have no idea if this is 'correct' but that is what he used).