M..Arch 1, for the unrelated backgrounds.

Although if you want to open a firm, I'd probably suggest a business degree and seeking clients in your own field first. Management is much harder than designing, especially when no one is paying the bills to keep work going.

bugsmetoo.. isn't interior design very related to architecture? 

I don't think I have the capability to study business, I want to focus on design only. I may figure out the management issue later. 

M.Arch 1:

For people who don't hold a B.Arch usually 3-3.5 years depending on the school. Some schools offer AP (advanced placement) for selected students, and let's you skip a year. With your current degree, this will be the only option regarding architecture programs in grad school.

 

M.Arch 2:

For People who received a B.Arch (who spent 5 years studying architecture in undergrad). Usually 1-1.5 years depending on the school.

M.Arch 3:

Never heard of it. Maybe it's just me.

This is how it is in the U.S. Not really sure in other countries.

 

Yes, interior design is very related to architecture, and it would become a great asset to have both skill sets and design ability in your hands. I have seen people go into business / planning / real estate / law programs in order to grab both design and management in the beginning. Now? they all seem to live happier lives (financially at least) than most architects, and some of them actually work in a field tangential to architectural / urban design. But very few actually went back to the design profession. Just sharing what I noticed from people I met in grad school.

I'd avoid the M.Arch 1, 2, 3 designations, as they're out of date (and previous poster got it wrong.)

You will need a NAAB-accredited M.Arch to be eligible for a license and to practice architecture independently in most states. The 1, 2, 3 designation refers to what ugrad degree a person has.

People with a non-architecture ugrad degree take 3-3.5 years.

Having a 4-year architecture ugrad normally takes 2 years for an m.arch.

An ID degree might get you some credit towards the m.arch so you don't have to go 3 yrs. They will review your transcript, even syllabi, and portfolio.

(Some schools offer a "postprofessional" m.arch, which is for people already with a NAAB-accredited degree. This degree in itself doesn't satisfy most state licensing reqs.)