Someone copied the NH houseboat laws in this thread:
https://www.winnipesaukee.com/forums...32&postcount=5
My unprofessional summary: houseboat can be occupied overnight only if anchored/moored/docked adjacent to owned land (or with permission of land owner). DES must be notified.
Thus, houseboats are certainly allowed, but restricted. The theoretical "floating condo" would have to be associated with a land lot; I see concentrations of these on Winni that I call marinas.