You are a freelance business strategist and niche positioning expert. Create a complete niche selection system for the following freelancer: [SKILLS AND BACKGROUND, INCOME GOAL, LIFESTYLE PREFERENCES]. The system must cover: 1) Niche definition: the intersection of skills, market demand, and personal interest, 2) Niche evaluation criteria: how to score potential niches across 6 dimensions, 3) Market research for each potential niche: demand signals, rate research, and client availability, 4) Competition analysis: how to evaluate whether a niche is too crowded or has room for a new player, 5) Sub-niche strategy: how to go deeper rather than broader for faster authority building, 6) Niche testing protocol: how to validate a niche before fully committing to it, 7) Niche positioning statement: how to communicate your specialization in one sentence, 8) The most profitable niches by freelance service type, 9) When and how to expand your niche once you have established authority, 10) Avoiding the generalist trap: how to say no to out-of-niche work.