Maryland PC or S-Corp, PLLC or LLC?

Hello.  I am  Maryland barred attorney who assists small business start-ups.

A professional corporation (PC) basically limits the scope of business activity to the specific licensed profession.  A PC may not issue stock to individuals not licensed in that profession, so your scenario proposed would not likely work.  It is not clear from your statement what area the other professional practices in. 

A "S-Corp" really refers to the taxation structure (it is  possible for a PC and/or a LLC to be taxed as a s-corp).   Each licensing board specifies how its licensees may practice.  In this state, architects may legally practice through corporations or  LLCs.

In any event, you will need to contact your governing board to inquire about obtaining a permit in the name of the entity (required whichever entity type you select).   Some professionals are limited in their ability to practice with others outside their profession, so I would also confirm this (through checking the stautes or calling your governing Board).  Assuming you have those preliminaries cleared, you should be free to select either a corporation or LLC (although you may want to talk with an attorney about the pros/cons of each or to get assistance in creating the entity and/or its governing documents).