Just finished reading an article on how freelancer got sued over Tweeting about late payments from their client. As a freelancer you need to protect your interests, and most of your work needs to be paid up front.
First time client need to up front the startup costs for working with me. These usually cover between 10 and 20 working hours. That is usually half of the time required to get the project done. Than the big check up comes after the first payment. Once a client pays up, you can safely assume that you sold yourself the right way, and that the client is solvent enough for your services.
This way you will weed out and eliminate all the people that are in the shady business of looking for free labor.
What if client is late with payment?
Than you are late with deliverables and you focus on finding better clients. Once the client pays the amount due, you can continue with delivering your quality work. You can write them professional email, explaining that their “subscription” has expired and that services will be extended when the due balance is paid. Act like a business.