Glad that you have got an idea to start your own firm, i am not sure that the licence and registration details but i can answer you for the second question.
You have a cold calling and search in the internet about the companies which are in your area mostly IT and non-IT firms, whose their recruitment team is inside and looking for an outsourcing consultancies like you are going to start. speak with them and take an appointment and meet them directly, speak with the HR or company head about your company information and tell them how you can help them.
before everything start you have your company website, official mail id's at least a group of people already on working (either freelance or part time also) a clear PPT about your company and services you are offering.
Now a days even small companies are also going for out sourcing for recruitment for very less percentage and margin, so research in market that what percentage that your fellow people or consultancies are following, go for recruitment agencies and as them whether they are interested for third party services.
i hope you know that you need to buy the search engines stuff before starting the agency, if not speak with naukri or monster people to help you,
once you got at least 1 or 2 clients per month, you and your fellow team can work from home itself and submit the profiles, i can advice you don't think about the company situation at now, you can put some dummy address and operate everything from home but relations and bonding between you and clients are important and everything is time based.
tell them that you can work for free for the first few requirements which are not so cost of recruitment, then they can commit for you and give you more importance and requirements than other clients.
keep in mind about agreement policies, documents needed for every time you meet with a client.
Even i am working for a business support for a dellhi based recruitment company in Hyderabad my job is i explained above,
main things are licence, search engine formalities, group of recruiters either (online or offline) and finally clients requirements.
our seniors can help you more on replying to you, call me if you need any thing on my reply 9989428443
all the best
11th July 2016 From India, Hyderabad