The amount a client pays is not the amount you keep. Between the two sit platform fees, payment costs, expenses and tax. Mapping them before you start helps you judge whether a side activity is worth your hours.
Platform and marketplace fees
Freelance platforms, marketplaces and app stores commonly keep a percentage of each sale, and some charge listing or subscription fees. Read the fee page of any platform you use and note the figures in your ledger.
Payment and withdrawal costs
Card processing, currency conversion and withdrawal fees can each take a slice. Payments from abroad may lose value in conversion and arrive days later.
Your own expenses
Software, equipment, materials, internet and transport are real costs. So is your time: divide what you keep by the hours spent, including unpaid hours for messages, revisions and admin.
Tax duties
In most countries, extra income must be declared, and it may affect your income tax or require registration as self-employed or as a small business. In Brazil, rules depend on the type and amount of income and on how you are registered. Because these rules change and depend on your situation, check the tax authority’s official guidance and consider talking to an accountant before your first payment.
A simple ledger
One table is enough to start: date, client or platform, gross amount, fees, expenses, net amount and hours spent. Keep invoices and receipts with it. A ledger kept from day one makes tax time calmer and shows honestly whether the activity covers its costs.
Limits
This note does not give tax figures or rates, which vary by country and change over time. Use it as a list of questions to take to official sources or a qualified professional.