However, you'll also find a few which are fee - based meaning they require a monthly or yearly subscription payment in order for you to continue using their services. (articlesfactory.com)
Depending on the project, participants may pay upfront or make subscription payments. (blog.aurorasolar.com)
Further, the $ 600 or $ 700 monthly subscription payment covers a comprehensive insurance policy, 24/7 roadside assistance, and complimentary routine maintenance. (autobytel.com)