Depending on the industry, freelance work practices vary and have changed over time. In some industries such as consulting, freelancers may require clients to sign written contracts. While in journalism or writing, freelancers may work for free or do work "on spec" to build their reputations or a relationship with a publication. Some freelancers may provide written estimates of work and request deposits from clients. Payment for freelance work also depends on industry, skills, experience and location. Freelancers may charge by the day, hour, a piece rate, or on a per-project basis. Instead of a flat rate or fee, some freelancers have adopted a value-based pricing method based on the perceived value of the results to the client. By custom, payment arrangements may be upfront, percentage upfront, or upon completion. For more complex projects, a contract may set a payment schedule based on milestones or outcomes. One of the drawbacks of freelancing is that there is no guaranteed payment, and the work can be highly precarious. In order to ensure payment, many freelancers use online payment platforms to protect themselves or work with local clients that can be held accountable.