For general information on Dominican legalities, see the FAQ section of another DR1 legal firm advertiser, Russin, Vecchi & Heredia Bonetti at www.rvhb.com This firm has a Puerto Plata branch.
We also recommend you contact Dr. Fabio Guzman, who advertises on this site, especially since he is located in Sosua. I believe he studied in Canada. He has been highly recommended by other message board contributors. You can reach him through his website at www.drlawyer.com
To answer your questions... No, you do not need citizenship. To start a business you do not need a visa. Many foreigners start a business without legal residence status, and then when they commit to living in the DR, they apply for residency. For the legalities on starting a business, see the rvhb.com web site business FAQ.