If you are talking about earth orbit artificial satellite or rocket launcher build then it is not one man job. It is collective effort. With small team you can build satellite in house by gathering different parts. First you will have to research and design the satellite and then you can order parts. Recently 2 Indian college have created satellites which were launched successfully on 22 June, 2016 along with ISRO's CARTOSAT-2C. Again it took 6-8 years to build these satellites for college students and their guide. Weight of payload or satellite matter's lot so it is important when you design and plan well.
For rocket build , it is restricted to only national approved agencies to do it. Research online for rocket design and manufacturing companies and eligibility required to get job there.