Ann. Laws of Mass. § 5.01(Registered Office and Registered Agent) says the following:
Each corporation shall continuously maintain in the commonwealth:
(1) a registered office that may, but need not be, the same as any of its places of business; and
(2) a registered agent who may be any of the following individuals or entities whose business office is also the registered office of the corporation:
(i) an individual, including the secretary or another officer of the corporation;
(ii) a domestic corporation or not-for-profit domestic corporation; or
(iii) a foreign corporation or not-for-profit foreign corporation qualified to do business in this commonwealth.
§ 5.02 (Change of Registered Office or Registered Agent) says:
(a) A corporation may change its registered office or registered agent by delivering to the secretary of state for filing a statement of change that sets forth:
(1) the name of the corporation;
(2) the street address of its current registered office;
(3) if the current registered office is to be changed, the street address of the new registered office;
(4) the name of its current registered agent;
(5) if the current registered agent is to be changed, the name of the new registered agent and the new agent's written consent, either on the statement or attached to it, to the appointment; and
(6) that after the change or changes are made, the street addresses of its registered office and the business office of its registered agent will be identical.
(b) If a registered agent changes the street address of his business office, he may change the street address of the registered office of any corporation for which he is the registered agent by notifying the corporation in writing of the change and signing (either manually or in facsimile) and delivering to the secretary of state for filing a statement of change that complies with the requirements of subsection (a) and recites that corporation has been notified of the change. If the street addresses of more than one corporation are being changed at the same time, there may be included in a single statement the names of all corporations the street addresses of the registered office of which are being changed.
Forms to be designated as a registered agent and for a company to change its registered agent can be found on the Mass. Sec. of State's Corp. Division website:
According to the statute, there is no special requirement for becoming a registered agent. You just have to be able to get companies to appoint you as their registered agent in Mass.
For much detail and free advice, you should contact an attorney with the Sec. of State's Corp. Division and ask for any help in getting in with companies as their registered agent. The phone number is(NNN) NNN-NNNN