Legally, it absolutely can be made in one contract: you can legally offer to purchase any number of different properties, assets, businesses, services, etc. via a single contract. It may not be a good idea, however, since the requirements and terms of a contract to buy a building and business are quite different, so that it may be difficult to encompass them in a single contract of sale. It may be better to have two contracts, but have each contract include a contingency (if you want) so that if the other deal falls through, you are not obligated to go ahead; i.e. the real estate contract could be made contingent on buying the business, and vice versa.