Unless you're working through an outsourcing company that offers inexperienced freelancers zero protection, you can stand up to these people without losing your mind. Some will test you and relish in the fact that they got under your skin deep enough so that you'll do anything to end the torture...like give your work away. This is a tactic I've experienced when I worked for oDesk (now Upwork) but even working remotely, you can lay down some ground rules.
The first step to avoiding problem clients is to not fall into their trap. When money's tight, this can be a difficult call but freelancing newbies must think about the future. While these few things don't make clients bad by default, it's just easier to keep things moving in a different direction when you encounter these scenarios.
They Request a Free Sample of Work
More than a decade ago, I applied for work at See's main offices as a data entry clerk. Though I'd passed the keyboarding test, they wanted to see how I interacted with others while working. It would only take an hour, so I thought 'Why not?' Not only did I get the job but I felt better knowing this was a large corporation and not some start-up or home kitchen office making this request.
This is why all freelancers need an online presence that promotes their work and credentials. If someone asks for a freebie, you send them the link to your profile/portfolio page and tell them to get back to you. Seriously, there's no need to debate this if the client is some unknown entity. If they are large (or respected in your industry), it's your call but hopefully, you have enough good references and online real estate to sell them quickly.
There are No Boundaries Established
A lot of new freelancers feel once they've come on board, they have no say in anything. That happened to me about 10 years ago when I had several streams of income, along with good references, but I was still happy for anyone who happened to "find" me. An overseas client learned about me and offered me work right away. Once I got my style guide and payment within a day, I was pretty content. However, when the holidays happened, I had to go into collector mode and realized I knew nothing about this client. As the weeks passed, I not only held off working for him but made the rounds to all of his contacts that payment was late and that I was considering legal action. By the end of the year, I got my payment but the relationship ended on bad terms.
Even if you work through an outsourcing company and something doesn't feel right, you can ask to set milestones. If the job is large, it's best to either ask for a percentage or a flat fee once a step has been completed. Sometimes, when clients decide to change the terms, you can also request at least a partial payment before going further. In this instance, it can't hurt to get the outsourcing company involved but if you don't have a little arsenal (like a lawyer or union), you can threatento report them to a governing agency that handles business deals gone bad. Some small business development corporations have legal assistance or resources that are free or low-cost for people that live in a designated area.
They are Slow-Paying
The good thing about this type of client is that you can drop them once you get a bigger job or expand your clientele. Some people tend to feel sentimental about letting go of someone who was there in the beginning stages but unfortunately, this isn't about your feelings. However, some people find themselves able to make some type of arrangement that's mutually satisfying.
You can either charge an extra fee for a faster turnaround or request that you'll finish the work at a designated time. If they fight you on this, you can explain that you have other clients or are tired of receiving late payments, or both. Normally, if your rates are reasonable (or you're willing to be flexible), they normally won't leave for greener pastures. Yet, sometimes, there are characters who do get off on taking hardworking freelancers through a bunch of changes with hopes the latter will settle the invoice at a reduced rate. They know they're wrong but don't let them manipulate you into doing something that can kill your business.
They Have a Bad Disposition...All of the Time
It comes with the territory, just like a regular job. All you can do is suck it up until it's time to take a vacation or wait until your roster has become so big you can literally pick and choose your clientele. Until then, just try to be a sweetheart unless they are outright verbally abusive towards you. Let them know early that you're not to be spoken to that way and that you will terminate the relationship if it happens again.
Like the above video states, a toxic client can have a domino effect on your business. Like that one "friend" that demands all of your time, energy, and existence knowing they're (or at least attempting to) keeping you all to themselves. Yeah, this type of individual has a problem but it doesn't have to be your problem.