Consultants charge people gobs of money for telling them stuff they already know. It's a pretty good racket if you can figure out how to get into it.

Well a master of science usually is not a professional degree, therefore you could not get licensed. I believe it would mean you are either :

A. Designing houses one at a time

B. Just a designer at a firm

C. Selling architectural products

But you would never be able to get a stamp or start your own firm without partners who are licensed. (this is all under the assumption of being in the USA and most jurisdictions) 

Some consultants that may be of use:

• Facade consultant (in projects where facades require advanced levels of engineering)
• Vertical transportation consultant  (tall buildings have complex systems)
• Hardware consultant (surprisingly more complex than it sounds)
• Signage consultant (the scope of this one can be huge)
• Security consultant (requirements for this can be very complex)
• Specification consultant (if you can't afford an in-house one)
• Code consultant (can be very helpful at times)

I could go on. The point is these people are capable of being extremely useful, or just be more trouble than they are worth. To become one of these, one requires high level of specialization. You do this by working for other specialists. Seems like a legit way of making a living.

Before we get too high-and-mighty in derogating consultants, remember that at another level every architect is a consultant --a paid expert. 

We tend to forget this because architecture is what we do all the time.  But in the context of a development project of any size, the architect is one (a really important one) of several consultants necessary to the process.

Consultants are functionally architects less burdened by an archaic fee structure.

In my world, an architectural consultant is pretty much an unregistered architect with their own practice.

A masters of science in architectural is a postgraduate degree in architecture and takes a total of 6 years of school, while a professional degree is a 5 year program. You can get an architectural license with either degree. You can't get a license with only a bachelors degree. Consulting architect doesn't really have a definitive definition. It can be anything from an individual who works independently as a sole proprietor of a small firm or a registered architect who is one of many at a larger architectural firm.

I know two people using that title: one is a code specialist to whom some local architecture firms outsource their code reviews, and the other is a sales rep for a window manufacturer.  Neither is a licensed architect so the title is actually illegal in this state, which prohibits use of "architect" and any variation on that word by unlicensed people.  Eventually the board will probably get hold of their business cards and hand-slap them with some fines.

It's not an absolute that you can't get licensed with an MS.  It's not an NAAB-accredited degree, but about half of US states have alternate routes to licensing, usually requiring some years of additional work experience. 

someone unemployed or retired...

it's the job you thought you'd have while still in architecture school! otherwise, i'd stick with 'retired' or 'unemployed' too. in any event, you still need to have an active state license to legally call yourself an 'architect' or use any derivation of the word in marketing your services to the public. 

Hi! Can anyone tell me what is the difference between architecture firms and the consultant companies? And also the difference between architects and consultants?

Architecture firms' main purpose is to orchestrate the production of the documents needed to construct a building, and keep the GC on track as he goes about construction.  Consultants have knowledge in various areas of expertise directly related to buildings (ie. zoning, accessibility, egress, curtain wall design, waterproofing, building code, historic building...) for which they are hired to provide this information.  For example, if you are working on a hospital, you might hire an architecture consultant with knowledge of accessibility design so you know that your project will have things constructed with proper clearances and mounting heights.  You can look into all the codes yourself, but this takes time you may not have.  Consultants are paid to expedite the necessary information.  They aren't necessarily licensed architects, but some are.