When determining your consulting fee, there are several factors to consider. Here are some key points to help you determine a reasonable rate:

1. Expertise and Experience: Your extensive experience and success in running multiple businesses with over 40 employees is valuable. Consider the value you bring to the table and the expertise you have gained over the years. Clients are willing to pay a premium for consultants who have a proven track record and can provide valuable insights.

2. Market Rates: Research the market rates for business consultants in your area or industry. This will give you a benchmark to compare your proposed rate against. Check out industry associations, online platforms, or even reach out to other consultants to gather information on typical rates.

3. Scope of Work: Assess the scope of work and the time commitment required to help your sister's friend. Determine if it will be a one-time consultation or an ongoing engagement. If it involves ongoing support, you may want to consider a retainer or a project-based fee structure.

4. Value Provided: Consider the impact your consulting services will have on her business. If you can help her make significant improvements or increase revenue, it justifies charging a higher fee. Think about the value you can bring to her business and how it aligns with her goals.

5. Competitive Advantage: As you mentioned, you genuinely want to see her succeed. Consider offering a discounted rate or a flexible payment structure as a gesture of goodwill. This can help build a positive relationship and potentially lead to referrals or future opportunities.

Taking all these factors into account, $30/hr seems quite reasonable for someone with your level of experience. However, it's important to remember that rates can vary greatly depending on the industry, location, and specific services provided. Ultimately, the fee you charge should reflect the value you bring and the market rates in your area.

It may also be helpful to have a conversation with your sister's friend to understand her budget and expectations. This will allow you to find a mutually beneficial arrangement that works for both parties.

Remember, as you gain more experience and establish yourself as a consultant, you can gradually increase your rates based on your expertise and the value you provide to clients.