Buying and selling - Import export

There is a firm in London, UK. Their business in simple words is the following. The firm is run by two brothers, who are property consultants in London. They buy property, make construction works, sell it with the margin. They are open for investors. Advantages of this possible deal: 1. Purchase of property, by contract. 2. Minimum 10% of annual profit is to be agreed in the contract. 3. Margin is agreed also in the contract (margin after selling the property). All legal. Safe investment in property. 4. Relativley safe and stable country.