Hi John,
From the NSF SBIR Phase I solicitation:
“The primary employment of the PI must be with the small business concern at the time of award and for the duration of the award, unless a new PI is named. Primary employment is defined as at least 51 percent employed by the small business. NSF normally considers a full-time work week to be 40 hours and considers employment elsewhere of greater than 19.6 hours per week to be in conflict with this requirement. […] A PI may be primarily employed at another organization at the time of submission, as long as he or she is primarily employed at the proposing small business at the time of award. A PI must devote a minimum of one calendar month of effort per six months of performance to an SBIR Phase I project”
So you would have to come up with a solution to have at least one person (the PI) to be working full-time for the small business concern during the Phase I. It is not required to have this set up when you are submitting your proposal, so you can stay employed elsewhere up until the start of Phase I if you are funded.
Let us know if you have any other questions, always happy to help!
Best,
Wout