Dash,
The only thing I would think about if taking payment via the website is on whether the price given to the customer is a quote or an estimate. If estimate, then it may be a good idea to ensure they cannot proceed unless they agree that they are aware of this.
Additionally, paypal being paypal, it is trusted which is good and has a number of API's to make use of. But paypal is and still remains more about buyer protection (despite advertising seller protection). As such it would be relatively easy for someone to defraud you and obtain their money back by unconventional means.
All I would recomend is that you get them to sign a form once the job has taken place giving their name, date and signature. Its never fool proof, but can help if ever you should be put in that situation.
Regards,
Tom.