Just one last thing to OP:
Why accept a payment option from your customers that could cause you to provide services for free?
Also, you're risking your PayPal and theirs to be frozen and money ceased for abusing the service.
Think of everything that people use PayPal for and now imagine it being permanently unavailable to you and/or that particular client. Considering it's the most widely used electronic money transferring/payment service in the world right now, it isn't even worth the risk to be unable to use it as some shopping sites, online stores, games, services, etc. only accept payment through PayPal. If you can't use PayPal anymore, you limit your access to online goods and services so drastically! Just don't do it, girl. It's not worth it at all. Find an adult friendly alternative or accept prepaid credit cards or e-gift cards instead. It's so much safer and the customer will never see your address, real name, location, etc. That's a privacy risk as well.
PayPal just isn't a safe payment option in general when it comes to person-to-person transactions vs. consumer-to-seller interaction (i.e. major companies like Apple and Samsung, for example) where your personal information doesn't matter whatsoever. Apple doesn't give a damn if you live in Phoenix, Arizona or Canada. They just want their money. Adult clientele can often have more sinister motives in some cases, to invest x-amount of dollars in exchange to being granted access and/or proof of your personal information (legal name, address, etc.) There's been plenty of cases where a model has accidentally released personal information to members (customers) by accepting gifts off of their Amazon Wishlist, where the member/customer was able to use a tracking number to find a model's location and even their personal address. Even if using a P.O. Box in a different city will compromise your approximate location assuming you don't go driving hours to pick up mail every few weeks. They see the location of the P.O. Box in a city that can most likely reveal that you live within an hour's drive of that particular city.
In my opinion, it is not secure or safe in any way to use services like this where a member ever gains access (accidentally or on purpose) to even your approximate location. Sure, most members aren't lunatics that are going to show up at the post office and wait for you to come collect your mail from a P.O. Box, but it has happened and I'm positive it will happen again. You just can't be too safe. No dollar amount or luxury is worth risking your personal safety for anybody under any circumstances, but that's just my opinion. You need to be aware of the risks of accepting off-site payments from members, especially for these kinds of services (adult work) in particular. You might end up giving a lot away for free by being scammed by members through PayPal, Google Wallet, Amazon, etc.
The only way to ensure payment for services is through the site you met the client on (assuming it's a camsite) by requiring payment up-front before any acts are performed for that specific member.