As of my last update in April 2024, here are some of the cheapest digital nomad visa options in terms of income requirements:

Mexico Nomad Visa:

Income Requirement: None. However, you must demonstrate economic solvency, typically by providing bank statements showing a minimum balance of approximately $27,000 to $36,000 for the previous six months. The exact amount may vary depending on the exchange rate and the specific requirements of the issuing authority.
Costa Rica Remote Worker Visa:

Income Requirement: Demonstrate a monthly income of at least $3,000 for a single applicant. For each dependent, an additional $2,000 is required. This can be a Costa Rican bank account deposit or guaranteed monthly income.
Czech Republic Freelance Visa (Živnostenský list):

Income Requirement: None. However, you must demonstrate sufficient financial resources to support yourself during your stay, typically by providing bank statements or other proof of financial means.
Portugal Remote Work Visa (D7 Visa):

Income Requirement: Demonstrate sufficient and sustainable income to support yourself and any dependents. The exact amount is not specified but should align with the country's minimum wage or higher.
Greece Digital Nomad Visa:

Income requirement: Effective January 1, 2023, demonstrate an annual income threshold of €35,000 for employees or €20,000 for freelancers. Based on the exchange rate in April 2024, this amounts to approximately $37,200 for employees and $21,200 for freelancers.
Please note that income requirements may change, and it is essential to consult the official sources for the most up-to-date information. Additionally, while these visas have relatively lower income requirements, other costs may be associated with the visa application process, such as visa fees, administrative expenses, and living costs in the respective countries.

Here are some additional tips to consider when exploring digital nomad visa options:

Research multiple destinations: Compare the income requirements, cost of living, and benefits different countries offer to find the best match for your financial situation and lifestyle preferences.
Consider remote work for foreign companies: If you work remotely for a company based outside your country of residence, you may not need a specific digital nomad visa. Ensure you comply with tax regulations and visa requirements for tourists or remote workers.
Explore freelance or contractor opportunities. Some countries have lower income requirements for freelancers or contractors than for employees. Consult with immigration specialists to understand the specific regulations for self-employed digital nomads.
Stay informed: Visa requirements and income thresholds can change over time. To stay updated on any changes or new visa options, regularly check official government sources and subscribe to digital nomad communities or forums.

It's important to note that the "cheapest" option may not always fit every digital nomad's needs and circumstances. Factors like duration of stay, work allowances, and ease of application process should also be considered.

Additionally, remember that the costs mentioned above are just the application/visa fees, and additional expenses may include legal fees, document translations, and other administrative costs.

When exploring digital nomad visa options, it's highly recommended that you thoroughly research each program's specific requirements, benefits, and limitations to determine the best fit. Consulting with an immigration specialist can also help you make an informed decision.