Long answer: The zone code for the municipality specifically identifies allowable uses in each zone.
I did not see a link to an online version of the zone code at the city website (http://cospnm.org/page2.php), but it might be there. The Community Development link (under City Departments) mentions a planning and zoning commission, and has contact information for their department. To be certain, you will need to review the zone code and pose the question to somebody at the city who has the authority to grant or deny your request.
I expect the R-1 zone, because it is typically very restrictive, will not allow businesses with onsite customers. The intent of most R-1 codes is to limit the intensity of use (traffic, parking, etc.) and preserve the residential character and attributes for all properties in the zone.
Another way to look at it.....If your house was in an R-1 neighborhood, would you want your neighbor to run a business and lease rooms to other businesses. Probably not.
Also, if you are getting a residential loan, your lender will likely require you occupy the property too.