Here's some advice about what to do if a client won't , or can't, pay. You completed your latest project on time, sent an invoice to your demanding client and are eagerly awaiting payment. . . and waiting. . . and waiting. . . and waiting.
Some clients feel free to pay late, others never pay at all.
Businesses usually pay their employees like clockwork because they know that if they don't the employees can complain to their state labor department, which can impose fines and otherwise make life miserable for them. However, this is not the case when you're self-employed. There is no government agency that will help you get paid. It's entirely up to you to take whatever steps are appropriate and necessary to get your clients to pay up. You should know that you don't have to accept this type of unethical behavior.