Photographs of the process, written logs, or testimonies from those involved can help.
He can be referred to as a "remote worker," "telecommuter," or simply someone "working from home."
Similar to employees, but focus on their experience, past projects, references, the tools they use, and their understanding of the project at hand.
While both terms imply working for oneself, "self-employed" is a broader term that includes business owners and entrepreneurs, while "independent contractor" refers to someone providing services under a contract without being an employee.
For personal residences, most home improvements like swimming pools, landscaping, and room additions are not tax-deductible. However, they might increase the home's cost basis, reducing potential capital gains tax when selling.