There is no right or wrong answer to whether it is better to have a set rate or a percentage-based pricing model for paid advertising services. Both approaches have their pros and cons, and the decision ultimately depends on various factors such as your business goals, target market, and competition.

Here are some points to consider when deciding between a set rate or a percentage-based pricing model:

1. Complexity and Effort: If your paid advertising campaigns require similar effort and complexity regardless of the client's budget, a set rate can be a simpler and more transparent pricing approach. This ensures that clients know exactly what they are getting for their investment and can help you avoid potential disputes over pricing.

2. Value-based Pricing: Consider the value you are providing to your clients through your paid advertising services. If you are confident that your campaigns consistently deliver significant results and a high return on investment (ROI), a percentage-based pricing model can be advantageous. This way, your fees align with the value you generate for your clients. For example, charging 10% of the ad spend as your fee would mean that the more successful the campaign, the more you earn.

3. Client Budgets: Take into account the budgets of your potential clients. If you primarily work with small businesses or startups with limited advertising budgets, a set rate may be more appealing and affordable for them. On the other hand, larger companies with substantial advertising budgets may prefer a percentage-based model as it allows them to scale their ad spend while keeping your fees proportional.

4. Market Competition: Research the pricing strategies of your competitors in the market. If the majority of your competitors are using a set rate, you may want to consider this approach to remain competitive. Conversely, if your competitors are mostly using a percentage-based model, it might be worth considering this option to align with industry standards.

5. Flexibility and Negotiation: Keep in mind that pricing models can be flexible and subject to negotiation. You can offer different pricing options to cater to various client needs and budgets. For instance, you could have a base set rate for a standard campaign and offer additional services or features at an extra cost. This allows you to accommodate different client requirements while maintaining a consistent pricing structure.

Ultimately, the most important aspect is to ensure that your pricing is fair, transparent, and aligns with the value you provide. Consider conducting market research, analyzing your costs, and experimenting with different pricing models to find the best fit for your business and clients.