Valuation as a science: Most investors look at a multiple called the P/E ratio (price to earnings ratio). In the global hospitality sector, the P/E ratio tends to be around 10 which means that earnings of USD 200,000 would imply that the business is worth 2 million dollars. 10% of this is 200,000 which means you're getting a good price. To get a better value, please substitute the P/E ratio of a similar business in your country and you should get the official valuation of the business.
Valutaion as an art: This would depend on factors such as industry outlook in your location, skills and synergy of the partners, sustainability of the business, growth prospects, brand value, property risk and other market risks etc etc. This approach is quite subjective becasue all the factors mentioned above are not measurable. Ultimately you will have to decide what your gut tells you after considering all the potential scenarios and outcomes.