Whether to pay for immigration help is really a question about your case, not about lawyers. A straightforward application, meaning continuous legal status, a clear qualifying job, and complete documents, is genuinely manageable alone in most countries, since official checklists have improved enormously.
Professional help earns its fee when complexity enters: previous refusals or overstays, criminal records however minor, employment gaps, self employment income, complex family situations, medical issues, appeals, or any case where a mistake costs years. Good advisers know how officers read files, spot weaknesses you cannot see, and their value is highest before submission, since prevention beats appeal.
Choose carefully, because this field attracts predators. Use only professionals licensed or registered under your country's system, verify them on the official register, and treat guaranteed approval promises or advice to misstate facts as immediate disqualifiers, since misrepresentation can bar you for years. And read everything before it goes in under your signature, because the file is legally yours.