If its an individual serviced site in an area that you want to build a house in, then its pretty straightforward and you just have to concern yourself with planning issues. If however its a site in a housing development (more likely), you are effectively helping a developer lay off some of his risk on a development that he is either over-stretched on, or that he doesn't have confidence in in the long term.
Unless you are an experienced builder or developer, and you are sure that you can build and sell on a house quickly, I would advise against this option. Working on someone else's development like this leaves you very exposed. This kind of business was a feature in Ireland back in the bad old days in the 1970s, when large developers put in roads and services and then effectively pushed the risk out to small players, some of whom survived and went on to great things, but many of whom had the opposite experience.