Earning $20,000 to $30,000 per month with an online business is certainly possible, but it requires careful planning, hard work, and dedication. Here is a detailed answer outlining some potential strategies and examples:

1. Identify a profitable niche: Research and identify a niche market with high demand and low competition. This could be anything from e-commerce, digital products, online coaching, consulting, or content creation. Look for areas where you have expertise or a passion to ensure long-term commitment.

2. Create a valuable product or service: Develop a product or service that solves a problem or fulfills a need within your chosen niche. This could be an e-book, an online course, software, or a unique physical product. Ensure your offering provides value and stands out from competitors.

3. Build a professional website: Establish a professional and user-friendly website to showcase your product or service. Use platforms like WordPress or Shopify to create an attractive and functional website. Optimize it for search engines and ensure it is mobile-friendly.

4. Implement effective marketing strategies: Utilize various marketing techniques to reach your target audience. Some effective strategies include search engine optimization (SEO), content marketing, social media marketing, email marketing, paid advertising (such as Google Ads or Facebook Ads), influencer collaborations, and affiliate marketing. Experiment with different channels to determine what works best for your business.

5. Focus on customer acquisition and retention: Implement strategies to attract and retain customers. Offer incentives, discounts, or loyalty programs to encourage repeat purchases. Provide exceptional customer service and actively engage with your audience through social media, email newsletters, or live chat. Satisfied customers are more likely to refer others, helping to expand your customer base.

6. Scale and diversify your income streams: Once your business starts generating revenue, focus on scaling and diversifying your income streams. Consider expanding your product line, launching a membership site, offering premium services, or exploring partnerships and collaborations. By diversifying your income, you reduce reliance on a single source and increase your earning potential.

7. Continuously analyze and optimize: Regularly analyze your business performance, track key metrics, and make data-driven decisions. Monitor your website analytics, conversion rates, customer feedback, and sales figures. Identify areas for improvement and optimize your marketing strategies and sales funnel accordingly.

Examples and references:
- Pat Flynn's Smart Passive Income (https://www.smartpassiveincome.com/) provides valuable insights, case studies, and strategies for building successful online businesses.
- Shopify's blog (https://www.shopify.com/blog) offers various articles and success stories related to e-commerce and online business.
- Neil Patel's blog (https://neilpatel.com/blog/) covers a wide range of topics related to online marketing, SEO, and business growth.

Remember, the journey to earning $20,000 to $30,000 per month requires patience, perseverance, and adaptability. It may take time to build a sustainable business, so stay focused, continuously learn, and adapt your strategies based on market trends and customer feedback.