For the very basics of what you'd need to adequately house a chameleon you'd need to budget thus:
Cage: $60-80 to start for a young animal, plus $100-150 a few months later to upgrade to a larger cage as the animal grows.
UV bulb: $20-50
UV bulb fixture: $20-50
Basking lamp and incandescent bulb: $15-25
Spray bottle: $5
Plants and cage decorations: $15+
Mineral/vitamin supplements and initial food: $20-40
Thermometer/hygrometer: $20-30
So for the most bare-bones, frugal setup you could realistically get going to keep a chameleon you're looking at an investment of at least $175-285 spent before you are even ready to begin contemplating buying an animal.
Furthermore, your weekly food costs for most animals will easily run you $5-10 per week, again being frugal, or about $260-520 per year just for food, not counting any additional costs.
Realistically, if you can't budget $200-300 for the setup, plus $300-600 per year in basic, ongoing costs for a total of $500-900 for the first year (and $300-600 per year thereafter), plus the cost of the animal, you simply cannot afford to have a chameleon. Even if you are being as frugal as possible, build your own cage, etc., these basic costs aren't going to drop much. Without at least a $500 budget to start, and a stead source of income, a chameleon is not for you.
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