Dear Mr. Paras,
Here is your checklist
1) It is better to be a certified Patent agent (exams conducted by IPO) - not mandatory ,else you have to get POA from your clients for Trademark related cases.whereas for the Patents you can do filing and drafting work for the clients(and make clients to do self application on their patents).
2) It is always better to have an Law Firm (it can be a proprietary firm) since you are going to deal with offshore clients.
3) Have a current account open on the Firm's name.
Wish you all the best.