Plan buying, pricing, and selling for my collectibles resale business

Help me plan the buying and selling side of my collectibles resale business. What I sell: [e.g. "sealed trading card products", "graded cards", "sneakers", "vintage toys", plus bulk or loose items] Where I sell: [e.g. "eBay", "TCGplayer", "StockX", "local shows", "my own store"] Current inventory: [ROUGH LIST with cost basis] Monthly sales and margin: [NUMBERS or "not tracked"] Cash I can invest: [AMOUNT] Time I can give it each week: [HOURS] Give me: 1. A profit-per-sale formula for each channel: sale price minus marketplace and payment fees, shipping and supplies, taxes I must collect if applicable, and cost of goods. Mark fee rates [CONFIRM CURRENT FEES]. 2. How to read the market: which price data to track (recent sold listings, not asking prices), release and reprint cycles, seasonality, and signals that a product is peaking or falling. 3. Buy and sell rules: a maximum buy price formula, target margin, when to hold vs sell, and a stop-loss rule for slow movers. 4. A plan for bulk or low-value inventory: lots, bundles, buylists, local sales, and whether it is worth my time per hour. 5. How to allocate my investment across restock, supplies, and tools, keeping a cash reserve. 6. Risk checks: counterfeits and resealed products, condition disputes, chargebacks, and over-concentrating in one product. 7. A simple weekly tracking sheet: Item | Cost | Listed | Sold | Fees | Net profit | Days to sell. Treat collectibles as volatile: do not predict prices, and remind me to invest only what I can afford to lose.