Hi Pako Gomez, I'm cutting and pasting here, so the following info is from another post on these forums, you can find that here:
"As the owner of a small interpreting company, I would give you the following tips:
1) A good interpreting company is one that is organized, gives great customer service, and pays its interpreters a fair wage and on time. You need to pay well to attract good interpreters.
2) A good place to start is contacting your local Administrative Office of the Courts at the State and Federal level. These are where the most highly qualified interpreters are located, and many often know interpreters in other languages.
3) The US Dept of State has a formal language testing and security clearance protocol. You can try to find interpreters who have this in their background.
4) If you yourself are an interpreter, try tapping into local interpreting/translating organizations (such as ATA and its local chapters), or NAJIT, which has a searcheable database of legal interpreters, many of which would have a clearance.
Basically the way you get started is by word of mouth- if you yourself are a good interpreter, you can start letting people know that you can find interpreters in other languages. It will take several years to build up your clients to the point where you can start hiring several interpreters. I would really make sure you have money saved up, invest in attorneys to draft up the contracts you will need, especially if you are going to be paying interpreters to travel and with security clearances, before you take the leap in establishing yourself as a "company.""
Remember that that information was not originally posted by me but I think its great advice. If you keep your interpreters and customers happy its a win-win situation for you.