We do not certainly want to discourage you but there are also things like zoning if you are going to do it our of your home. Depends on where you live! But to do gun repair or act as a service shop you will have to have the FFL License as the others have advised. In addition you will have to log in and out each weapon in your Fed Books. They are getting very picky about this especialy after the Feds Fast and Furious debauchery!!!!!
The Constitution is not an instrument for the Government to restrain the people. It is an instrument for the people to restrain the Government!
“Americans have the right and advantage of being armed. Unlike the people of other countries, whose leaders are afraid to trust them with arms.”
James Madison. Author of the 2nd Amendment