An unmarried partner cannot receive TD status. If he is her spouse and obtains TD, he may live with her and study but may not work, including by running a business from a U.S. address. To operate a U.S. business, he needs his own work-authorized route, such as E-2 based on his own qualifying investment.
Choosing the principal
This household has two working adults, and marriage changes the derivative analysis. If she is the TN principal, an unmarried partner has no TD eligibility; if he is her spouse, he may hold TD but may not work, and managing his Québec contracting business remotely from a U.S. apartment is work whatever the payroll says.
If instead he becomes an E-2 principal on a franchise territory, only a spouse may obtain E-2 derivative status and become employment-authorized incident to that status. Both adults could also hold their own principal statuses at the same time, TN for her and E-2 for him, which requires two complete files and does not depend on marriage. Children may study in either dependent status and cease to be eligible at 21.
Set the available options side by side with dates before either adult signs anything, and note that a person who holds Canadian permanent residence but a treaty-country passport could be an E-2 principal but never a TN one.